- Open Access
Sluggish cognitive tempo and its neurocognitive, social and emotive correlates: a systematic review of the current literature
Journal of Molecular Psychiatryvolume 2, Article number: 5 (2014)
Since the elimination of items associated with Sluggish Cognitive Tempo (SCT) during the transition from DSM-III to DSM-IV from the diagnostic criteria of Attention-deficit Hyperactivity Disorder (ADHD), interest in SCT and its associated cognitive as well as emotional and social consequences is on the increase. The current review discusses recent findings on SCT in clinical as well as community based ADHD populations. The focus is further on clinical correlates of SCT in populations different from ADHD, SCT’s genetic background, SCT’s association with internalizing and other behavioral comorbidities, as well as SCT’s association with social functioning and its treatment efficacy.
A systematic review of empirical studies on SCT in ADHD and other pathologies in PsycInfo, SocIndex, Web of Science and PubMed using the key terms “Sluggish Cognitive Tempo”, “Cognitive Tempo”, “Sluggish Tempo” was performed. Thirty-two out of 63 studies met inclusion criteria and are discussed in the current review.
From the current literature, it can be concluded that SCT is a psychometrically valid construct with additive value in the clinical field of ADHD, oppositional defiant disorder (ODD), internalizing disorders and neuro-rehabilitation. The taxonomy of SCT has been shown to be far from consistent across studies; however, the impact of SCT on individuals’ functioning (e.g., academic achievement, social interactions) seems remarkable. SCT has been shown to share some of the genes with ADHD, however, related most strongly to non-shared environmental factors. Future research should focus on the identification of adequate SCT measurement to promote symptom tailored treatment and increase studies on SCT in populations different from ADHD.
The current literature review gives an overview about the research performed on the concept of Sluggish Cognitive Tempo (SCT). SCT is a cognitive-emotional style that is commonly described by five typical characteristics, which are “daydreaming”, “being confused”, “staring blankly”, “being sluggish” and “being unmotivated” [1, 2]. SCT was originally introduced in the literature on ADHD but is nowadays recognized in disorders different from ADHD as well [3–5]. The Diagnostic and Statistical Manual of Mental Disorders (DSM-IV and DSM-5) distinguishes three different subtypes of ADHD, namely ADHD combined type (ADHD/C), ADHD predominantly inattentive (ADHD/I) or ADHD predominantly hyperactive/impulsive (ADHD/HI) . The transition from the 3rd to the 4th edition of the Diagnostic and Statistical Manual of Mental Disorders , however, led to the removal of items representing sluggishness, easy confusion, and daydreaming from the inattention dimension of ADHD  due to poor predictive validity . Regardless of the increasing interest in symptoms of sluggishness in ADHD during the last two decades [10–13] the current DSM-5 has not reintroduced the items representing a sluggish cognitive-emotive style. Based on recent psychometric findings, however, it is argued that the elimination of SCT symptoms during the transition from the DSM-III to the DSM-IV artificially increased ADHD’s homogeneity [14, 15]. As a consequence, it is hypothesized that some of the individuals who actually would have met diagnostic criteria of one of the ADHD subtypes are missed due to the elimination of SCT items.
Especially, ADHD/I has been frequently linked to symptoms such as, daydreaming, staring, mental fogginess, confusion, hypoactivity, sluggish or slow movement, lethargy, apathy and sleepiness [6, 15–19]. It is striking that the mentioned symptoms are very similar to items currently used in the measurement of SCT. In line with this, 30 to 50% of the children diagnosed with ADHD/I have been shown to present with increased levels of symptoms that emerged under the label SCT . Based on the observation that approximately twice as many school-aged children are nowadays diagnosed with ADHD/I in contrast to ADHD/HI [21, 22] and ADHD/I’s strong association with SCT, there is a need for a thorough definition of SCT’s cascading effects on individuals’ functioning. This being said, the current literature on SCT is rather inconsistent in terms of the definition and measurement of SCT. No consensus has been met, yet, with regard to symptomatology or standardization in the assessment of SCT. Neurocognitive impairments that are seen in children with ADHD/I with comorbid SCT but not in children with pure ADHD/I further show that even though SCT is very similar to ADHD/I, SCT has its own neurocognitive characteristics [6, 17, 23, 24]. A thorough look at the diagnostic validity of SCT and its impact on a variety of individuals’ functional domains seems therefore to be warranted. Furthermore, given the heterogeneity in the measurement of SCT and its inconsistency in the definition of the concept SCT, treatment approaches of SCT are, so far, rather sparse. Yet, given the outlined neurocognitive characteristics that are typical for SCT but not ADHD [6, 17, 23, 24], treatment that is independent of a possible comorbidity of ADHD seems to be important. The presence of SCT symptoms above and beyond ADHD symptoms might be one of the mediating factors in treatment efficacy in psychiatrically referred individuals.
During the process of the review another review on the same topic was published . In contrast to Becker  the current review discusses findings on SCT in adults, genetic studies, gender differences, SCT in disorders different than ADHD [3–5], specific treatment of SCT and stresses the current lack of standardization in the assessment of SCT. Each section of this review will be dedicated to one of the functional domains that have been shown to be affected in individuals with SCT. It was our aim to dissect the unique contribution of SCT to impairments, whenever the reviewed studies’ designs allowed for such a conclusion.
A systematic review of the English published literature of several databases (PsycInfo, SocIndex, Web of Science, PubMed) on the key terms “Sluggish Cognitive Tempo”, “Cognitive Tempo”, “Sluggish Tempo” revealed a total of 63 articles of which 32 (see Additional file 1: Table S1. Studies and measures employed) were closely related to SCT and will be reviewed in here. Inclusion criteria were: SCT was measured by questionnaire or observation and its relation to neuropsychological, emotional or social functioning was tested. The remaining 31 studies were not included in this review since SCT was not systematically assessed or the focus was on age-related cognitive slowing or learning (e.g., reading) ability and its relation to cognitive tempo. The majority (92%) of the studies focused on SCT comorbid to ADHD symptoms as a personality trait or clinical disorder.
Lack of standards in the measurement of SCT
Current studies on SCT predominantly focused on SCT in children and/or adolescents with either traits [11, 26] or clinical diagnoses of ADHD [10, 27]. Only one study looked into SCT in adults with ADHD, examining hereby the association between self-rated SCT and executive functioning . Initially, SCT was represented by four items (“difficulty following instructions”, “sluggishness”, “drowsiness”, “absent-minded, forgetful” ) that were then either reduced to two (“daydreams”, “is low of energy” [12, 17, 29–31]) or expanded up to 17 items in more recent studies [19, 32, 33].
Penny and colleagues  addressed the lack of agreement in standardised measures in SCT and came up with a unique SCT questionnaire based on items that have been shown to load highly on SCT in previous research [14, 19]. An extensive review of the literature on available items measuring SCT with subsequent reliability and factor structure analysis decreased the initial pool of 26 items to a 14-item SCT scale (see Additional file 1: Table S1 for individual items; ). In contrast to Penny’s 14 item scale, Skirbekk and colleagues  compared the utility of Pfiffner and colleagues’  17-item scale (SCT-17 see Additional file 1: Table S1 for individual items) to a 5-item scale (SCT-5 see Additional file 1: Table S1 for individual items) by Hartman and colleagues  and showed that both scales capture the concept of SCT [23, 27, 34] but add to Penny and colleagues’ scale the dimensions of confusion  or forgetfulness (SCT-15 ). According to Penny and colleagues , the items measuring the concept of confusion (i.e., forgetfulness, disorganization and difficulty following instructions) were explicitly removed as they are part of the ADHD DSM-IV criteria and nowadays DSM-5 criteria of inattention. Moreover, Hartman and colleagues  showed that their five SCT items (SCT-5) loaded strongly on the same factor that was identified to represent cognitive and physiological sluggishness by the more extensive Child Behavior Checklist (CBCL ), contributing further evidence of adequate convergent validity of their 5-item SCT scale. The presented findings indicate that it appears not to be the number of items that matter in measuring SCT but the items’ representativeness, with the short 5-SCT scale of Hartman and colleagues  being a promising tool in diagnosing SCT in the pediatric setting. Whether the 5-SCT scale by Hartman and colleagues  would outweigh the utility of Penny and colleagues’  14-SCT scale is yet to be investigated.
To conclude, even though various scales have been shown to effectively measure SCT [16, 31, 36], a standard of measurement across studies is not yet achieved. Moreover, some evidence points into the direction that even though SCT items might identify individuals with SCT [2, 11, 14], their contribution in distinguishing subtypes of ADHD should be questioned [13, 30]. Independent of the number of items that were used to represent SCT, “daydreaming”, “sluggish/drowsy” and “underactive/apathetic” were items that consistently contributed to the identification of SCT in children [2, 11, 14, 19] and adults . More in detail, the item “daydreaming” was represented in all studies reviewed [23, 27, 29, 34] followed by “sluggish/drowsy” [16, 30, 31, 36] and “underactive/apathetic” [11, 16, 23, 37]. Future research could use these three items as a baseline measurement for SCT without missing out to assess their individual link to behavioral and neurocognitive correlates.
A consequence of the lack of standardization in SCT measurement reinforced the discussion about whether SCT is a disorder itself above and beyond ADHD [6, 11, 16, 19], or whether SCT is comorbid to, or a subtype of ADHD [13, 17, 36, 38]. The following section is dedicated to this issue and will give more insight into the comorbidities of SCT.
SCT and its link to ADHD subtypes
To start with, not only SCT is questioned for its diagnostic value in and above ADHD but so is ADHD itself. One of the current debates concerning ADHD focuses on the question whether ADHD should be handled as a continuum or as a clear-cut category of behavioral, cognitive and emotional deficits [1, 30]. Supporters of the former thesis welcomed the increase in studies focusing on SCT in ADHD and tested the contribution of SCT in diagnosing ADHD [1, 30]. Evidence was found that SCT not only enhances the reliability of diagnosing ADHD [19, 30, 36] but also contributes to the identification of a new subtype of ADHD  or a disorder itself [6, 11, 16, 19]. It is currently hypothesized that the SCT construct captures attentional deficits that are not represented by the nine symptoms measuring inattention according to the DSM-IV (as well as DSM-5) guidelines for ADHD/I [19, 33]. The endorsement of sleepy/sluggish and slow/daydreamy symptoms were shown to be more likely to be associated with ADHD/I than with ADHD/C or ADHD/HI [1, 10, 13, 17, 23, 29, 38], supporting the idea that the inclusion of the SCT items in diagnosing ADHD might enhance the reliability of ADHD/I diagnoses [19, 36]. In line with this, SCT subscales have been shown to present with both, good discriminant validity with symptoms of hyperactivity and strong convergent validity with symptoms of inattention . McBurnett and colleagues  showed that when SCT symptoms were tested in ADHD/I [1, 10, 36], the SCT items did not show the extremely poor loading that ultimately led to the exclusion of SCT items from the DSM-IV [8, 9]. It can be concluded, that the inclusion of SCT items in the identification of individuals with ADHD/I seems therefore valuable. At the same time, it can be reasoned that when SCT contributes to a more defined subtyping of ADHD/I it also (indirectly) enhances the number of ADHD diagnoses. This is in line with the former proposed argument that excluding SCT from ADHD criteria might lead to missing out on individuals that would otherwise be diagnosed with ADHD/I [19, 36].
In contrast to accumulating evidence that SCT item inclusion enhances the number of ADHD/I diagnoses [13, 17, 38], no difference in SCT were found in children with ADHD/I and ADHD/C [13, 27, 33] or in class room observations of children with behaviour of ADHD [30, 34]. Expanding the association of SCT with ADHD or ADHD/I to ADHD common comorbidities, Skirbekk and colleagues  found that children with anxiety comorbid to ADHD exhibited the highest levels of SCT, followed by children with exclusively ADHD and finally children with clinical levels of anxiety compared to children with neither anxiety nor ADHD . Unfortunately, children were not further subtyped into ADHD/I, ADHD/C or ADHD/HI, complicating thereby the comparison of findings across studies. Nevertheless, the presence of the highest SCT symptoms in children with anxiety and ADHD supports the idea that not merely ADHD is affected by SCT but SCT might be present in ADHD comorbidities in general and emotional disorders in particular. Further evidence that SCT can be found in disorders different from ADHD is given in the following section.
SCT is not ADHD but a disorder distinct from ADHD
SCT has been shown to not only be present in children with ADHD [2, 33] but also in children who do not meet ADHD criteria . Findings that SCT and ADHD/I relate differently to symptoms of inattention [6, 11, 19] underline the idea that SCT is a disorder itself and not merely comorbid to ADHD/I. Moreover, SCT emerged as a separate psychometric valid construct during data analysis in children that did not reach ADHD thresholds of DSM-IV criteria but presented with clinical symptoms of behavioural/emotional and/or learning difficulties . The idea that SCT might relate to attentional impairments in clinical groups in general led Reeves and colleagues  to assess the presence and relationship of SCT to later cognitive outcomes of pediatric survivors of acute lymphoblastic leukemia. Lymphoblastic leukemia survivors were successfully identified from their healthy siblings by SCT. Moreover, SCT related to the survivors’ intellectual and achievement deficits . Similarly, SCT was found in children diagnosed with Fetal Alcohol Syndrome (FAS) with and without comorbid ADHD and in children with clinically behavioral deviance . SCT was found to be statistically linked but distinct from ADHD in a large sample of clinically distressed children . The items “being confused”, “daydreaming”, and “stares blankly into space” related to internalizing and social deficits, as well as behavioral problems independently of ADHD or other psychopathologies in psychiatrically hospitalized children . It can be concluded that SCT is not only a valuable factor in the clinical assessment of children or adolescents with ADHD but might be a valuable factor to look at in pathologies different from ADHD [3, 4, 13].
SCT etiology: environment vs. genetics
Based on the observation that SCT was typically associated with ADHD, and ADHD has been shown to be highly heritably (additive and dominant genetic effects of around 75% for ADHD; ), researchers became interested in SCT’s genetic background. A recent twin study showed that the association between SCT and ADHD/I was almost twice as strong as the association between SCT and ADHD/HI . While genetic factors were shown to be of particular significance in hyperactive-impulsive behaviour in general, the non-shared environmental factors were the major factor likely to explain individual differences in SCT . Accordingly, the association of SCT with ADHD/I was found to be partly due to genetic (r = 0.29) and partly due to non-shared environmental factors (r = 0.21), whereas the association of SCT with ADHD/HI was almost purely attributable to genetic factors . These findings indicate that SCT, even though it is genetically related to ADHD, is the least heritable subtype among ADHD . SCT’s special association with environmental factors, led the authors to suggest that SCT might develop due to the environment created by facing ADHD symptoms . Moruzzi and colleagues’ pioneering work should be carried on in a population in which SCT symptoms are the main reason for being referred to a clinician. If similar neurocognitive and or behavioural SCT symptoms exist between individuals who are seen for their SCT symptoms only and those with other comorbid conditions (such as ADHD or other pathologies), symptoms should be further tested for their genetic vs. (psychopathological-) environmental background.
SCT’s cognitive and neuropsychological correlates
SCT’s association to various cognitive and neuropsychological correlates has been one of the major interests in the last decade of research in the field of ADHD. Whereas earlier studies suggested that children with SCT present with slow motor and processing speed [6, 15, 17, 28, 38] more recent studies could not replicate a link between SCT and processing speed . The studies which reported such a link [15, 17, 28, 38] are based on the assessment of individuals with ADHD/I that are characterized by high levels of SCT, whereas Bauermeister and colleagues  focused on individuals with pure SCT and its impact on information processing. Furthermore, the majority of studies reporting an association between SCT and slowed information processing [15, 17, 28] did not make use of neuropsychological/behavioural assessments of cognitive tempo, but refer to teacher and parent observations only (e.g., the child seems to be “lost in a fog”, “daydreaming or getting lost in thought,” and “apathetic or unmotivated”). It has to be questioned whether behavior observations reliably reflect slow processing speed or whether reductions of processing speed are better depicted by actual assessments using psychometrically valid information processing tasks, such as reaction time measures, visual search- and pattern recognition tasks, or perceptual timing tasks. Experimental data indeed confirmed that children with ADHD/I and SCT presented with a slower task accomplishment during the Tower of London Task (ToL) and higher mean reaction times in the Continuous Performance Test [31, 40]. The authors concluded that children with ADHD/I and SCT do not present with inaccurate performance but do perform neurocognitive tasks in a conspicuous slow tempo . It has therefore been hypothesized that SCT does not affect the underlying cognitive function per se (e.g., EF, inhibitory control) but compromises the overall task performance by slowing down task related processes .
Solanto and colleagues , however, did not control in their study for the children’s attentional functioning. Especially deficits in sustained attention have been found to be related to SCT [24, 27, 33]. The reason why some studies failed to confirm attentional deficits in children with SCT [17, 41] might again be that subjective teacher ratings based on class-room observations are not sufficiently sensitive and valid and by this miss relevant aspects of the children’s attentional problems. While studies applying neuropsychological tasks, such as classic vigilance, divided attention and selective attention tasks, revealed no differences in attention between ADHD subtypes [41–43], a unique association was found between SCT and early selection deficits in a perceptual load paradigm . For an overview of the exact neuropsychological tests applied, please view Additional file 1: Table S1. Children with ADHD and comorbid SCT showed more interference on early selection tasks than children with ADHD but without SCT . Deficits in sustained attention of individuals with SCT were further explained by an increased variability in spatial memory performance . It seems likely that other functions, such as EF or inhibitory control as reported above (see discussion of ), might also be deviant due to sustained attention deficits rather than processing speed.
Barkley  recently showed that SCT symptoms explained unique variance of self-rated executive functioning (EF) independent of the impairments associated with ADHD/I or ADHD/HI. These results, however, could not be replicated in a younger sample of children scoring high on ADHD and SCT . Furthermore, behavioural ratings of EF in adolescents were also found to be unrelated to SCT but associated with ADHD/HI symptomatology . These inconsistencies in findings might result from different assessment strategies applied (self-rated vs. observer-rated) and different age groups assessed (children vs. adolescents vs. adults) in the mentioned studies [5, 11, 16]. With regard to the differences in age between the samples it has to be considered that EF is known for its developmental trajectory . More in detail, EF was shown to be relatively mature at the age of 12 but knows a transitional period of development at the beginning of adolescence . It therefore can be speculated that the adult sample of Barkley  was much more aware of their EF deficits and, hence, more likely to report them than the observer-rated younger participants of Bauermeister and colleagues  and Becker and colleagues . Furthermore, previous research has shown that EF self-ratings are more sensitive to particular EF related symptoms than neuropsychological tests . However, as Barkley  did not control for the impact of comorbid ADHD subtypes it remains open whether the association between SCT and EF was unaffected by the underlying ADHD symptomatology.
Studies that controlled for ADHD/I symptomatology in order to show the unique impact of SCT on attentional functioning support the idea that SCT is associated with more severe attention deficits than ADHD/I . Moreover, SCT related to sustained attention deficits that were not seen in ADHD/I . The established link between SCT and attention deficits [24, 41] might lead to the suggestion that individuals with SCT are in general more prone than individuals with ADHD to perform worse on neurocognitive tasks and experience more deficits in everyday functioning. This knowledge appears relevant for the treatment of SCT because attentional functioning has been shown to be one of the core factors predicting rehabilitation outcome [47, 48], including treatment efficacy and socio-cognitive functioning in general [47, 48]. Research confirming a link between SCT and poor cognitive outcome [4, 13] further underlines the need for research on SCT in neuro-rehabilitation populations. To support this, SCT has been proposed to be the behavioral manifestation of slow processing speed , with slow processing speed being one of the rather common cognitive late effects after acquired or developmental neurocognitive pathologies in general . Research on SCT in neuro-rehabilitation populations seems therefore warranted.
SCT and internalizing symptoms: SCT’s relation to depression and anxiety
Lahey  was one of the first who reported differences in comorbidities according to ADHD subtypes. Whereas ADHD/C is more likely to be associated with externalizing behavior, ADHD/I appears more often to be linked to internalizing symptoms, with both types of ADHD also being related to conduct disorder (CD) . After removing children with CD from their analysis, cognitive tempo was the most distinguishing factor between ADHD/C and ADHD/I . Lahey  therefore concluded that except for the cognitive tempo factor, other symptom differences in ADHD might be due to other comorbidities than SCT, such as externalizing and internalizing. Given that SCT is foremost believed to be associated with ADHD/I, SCT’s proneness to internalizing behavior seems to be comprehensible.
Consequently, recent research confirms the link between SCT and internalizing symptoms such as anxiety and depression [2, 8, 11, 13, 17, 37], with some authors claiming that SCT is stronger related to depression than to anxiety [5, 36] even though correlations of SCT with depression were rather modest . Comorbidity of internalizing disorders was based on validated rating scales such as the DISC-IV [5, 37], the Emory Combined Rating Scale (ECRS)  or the Impairment Rating Scale (IRS) . Moreover, clinically referred children with severe SCT presented with increased symptoms of depression, a greater risk for generalized anxiety, social phobia and obsessions than children with low SCT . The authors concluded that SCT is more likely to go along with internalizing disorders, such as depressive disorders and generalized anxiety disorders, than ADHD . However, SCT has been shown not to be merely a measure of depression but to be statistically distinct from depression [5, 36]. Furthermore, internalizing problems correlated with SCT independently of ADHD inattention problems , leading to the assumption that SCT knows its own internalizing dimension that is not linked to ADHD symptomatology [2, 11].
With regard to anxiety it has been shown that the association between SCT and symptoms of anxiety is mediated by symptoms of inattention . The authors hypothesized that anxiety disorder comorbid to ADHD decreases individuals’ attentional capacities even further . The decrease in attentional capacities by anxiety is further believed to make individuals more vulnerable to leave the impression of being sluggish and slow . However, it seems likewise probable that ADHD with comorbid SCT makes individuals more prone to develop a depressive or anxiety disorder [27, 33]. For example, a similar association between SCT and internalizing behavior was observed in clinical populations suffering from ADHD and SCT  as well as in populations with SCT and a clinical condition different from ADHD (FAS ). Furthermore, anxiety and depressive symptoms of clinically-distressed children correlated with levels of SCT, even beyond the ADHD/ODD symptomatology . Notably, SCT levels were found to be stronger related to depression than to anxiety symptoms when parent-ratings were controlled for the parents’ own anxiety and depressive symptoms . Becker and colleagues’ findings indicate that the raters own mental constitution should be taken into consideration when interpreting results from ratings that are not directly derived from the target population (e.g., no self-rating measures).
In contrast, the findings of studies focusing on SCT’s impact on externalizing, disruptive behavior, which is often seen in ODD, are rather promising . For example, Wåhlsted and colleagues  showed that behavioral symptoms of SCT were not associated with internalizing problems but showed an interaction with inattention and ODD in a community sample of children. In more detail, more severe SCT decreased the likelihood of ODD symptoms in children with very distinct symptoms of ADHD symptoms [24, 27]. Furthermore, high levels of SCT were shown to be related with low levels of disruptive behavior , making SCT a protective factor against ODD symptomatology in children with ADHD [17, 20, 23].
It can be concluded that even though SCT seems to be related with internalizing, emotive disorders, its unique interaction with other comorbidities should be disentangled first. Moreover, whereas SCT can be interpreted as a risk factor per se, making individuals more prone to depression, SCT has also been shown to lower individuals’ risks of severe disruptive behavior.
SCT and other characteristics: SCT’s link to academic functioning, gender, age-of-onset
SCT has been demonstrated to be further associated with academic outcomes in general , math , linguistic processing deficits  and initiative taking as well as motivation in particular [10, 36]. It has been shown that especially low levels of initiation and persistence in clinically referred children with ADHD and SCT contribute to the impairments seen in academic achievements . Furthermore, math scores did not only negatively relate to ADHD symptoms of inattention but also to SCT . It was shown that SCT beyond symptoms of inattention and hyperactive-impulsive symptoms relate to academic achievements [11, 50]. However, when relying on parent ratings of SCT, a link between SCT and academic achievements as was seen in teacher ratings [11, 50] could not be confirmed . The observation that teacher and parent ratings of SCT yield different results with respect to SCT’s impact on academic functioning calls for thorough investigation of to what extent findings on SCT and its correlates are affected by within- (SCT levels and correlates assessed by same rater-population) versus between-context ratings (SCT levels assessed based on ratings of observer population A but correlates of SCT rated by observer population B).
With regard to other socio-demographic variables, it has been observed that gender ratios differed according to ADHD subtype and SCT diagnosis . Todd and colleagues  showed that SCT item loadings were different for males and females. Accordingly, two SCT items (“day dreams”, “low energy”) were identified to form a separate factor in boys (explaining 6.6 % of the total variance) but not in girls. In girls, the two SCT items (“day dreams”, “low energy”) loaded on the inattentive factor of ADHD/I. The authors concluded that boys with ADHD and SCT are best described by an inattentive and a hyperactive-impulsive factor, whereas girls’ subtyping was not facilitated by the inclusion of SCT symptoms . However, Garner and colleagues  showed that SCT symptoms were generally increased in boys prone to behavioral deviance and/or individuals with an ADHD/I diagnosis. Various research on ADHD shows that ADHD is more closely linked with being male than female. Male-to-female ratios of ADHD diagnosed individuals have been shown to range from 9:1 to 6:1 , with community-based samples presenting with a ratio of approximately 3:1 . Research on gender differences in ADHD is, however, highly needed . Not only should attention be drawn on methodological limitations such as gender-biased diagnostic tools, but also on the possibility of confounding effects due to referral biases . For example, girls from community-based samples of ADHD presented on average with lower levels of inattention, internalizing behavior and peer aggression than boys with ADHD, whereas clinical samples of ADHD did not show any differences on these variables for gender . It should be questioned whether differences in gender on SCT and ADHD are a mere effect of referral-bias or whether future research should handle different standards in evaluating SCT and ADHD in line with the individual’s gender.
With regard to mean age of symptom-onset of SCT, no differences were found between ADHD samples with low SCT and high SCT . Bauermeister and colleagues , however, found a later onset of inattention and SCT symptoms in their group of individuals with inattention. However, it remains unclear whether these differences in mean onset age of symptoms are indeed due to differences in samples or simply due to a distortion associated with retrospective assessments of ADHD/SCT symptoms. Moreover, Bauermeister and colleagues’ sample  was characterized by a low impairment in adaptive functioning and the assessed mothers reported only little to no child-related family stress. The results of Harrington and Waldman , in contrast, stem from clinically referred children who were seen due to their suspiciousness for attentional and behavioral deviances. It can be speculated that the onset time of symptoms is either better remembered for those who are suspicious of severe behavioral deviance  compared to those who are rather adapted  or that the onset of symptoms indeed differs due to differences in symptom severity.
SCT and social functioning
Within the last decade the interest in ADHD diagnosed individual’s social and emotional functioning is on the increase [54–57]. It was already mentioned above that individuals with SCT are more prone to internalizing behaviors [2, 5, 8, 11, 13, 17, 37, 51], such as turning inward, not expressing certain needs, and appearing rather shy. Internalizing behaviors have been further shown to increase the proneness of being less socially interactive. It can be assumed that a decreased opportunity for social interactions might affect social functioning in general and vice versa. In line with this, it was shown that children with ADHD/I with SCT tended to take less initiative in social situations and were rated to be less assertive and more self-controlled during home and school based observations . This finding was not replicated in a later study in which inappropriate on-task behavior was found to be unrelated to SCT but associated with symptoms of inattention . While both studies [11, 12] used information obtained from behavioral observations during task performance  or class-room performance  to measure social functioning, the authors failed to implement a standardized measure of social functioning.
Mikami and colleagues  in contrast applied computer simulated peer interaction in order to measure social skills of children with ADHD and SCT compared to different ADHD subtypes. In line with the observation that children with ADHD/I and SCT have more social problems, are more likely to be socially withdrawn [17, 51], less happy and more anxious in social interactions , Mikami and colleagues  found fewer responses, a weaker memory and a reduced ability to attend to subtle social cues in children with ADHD/I and SCT compared to children with ADHD/I without SCT. Moreover, a relation between SCT and children’s hostility was observed  with children suffering from ADHD/I and SCT showing less symptoms of hostility than the group of children with ADHD/I but without SCT . A reduced hostility of children with SCT was further confirmed by Becker and colleagues , supporting the formerly proposed positive impact of SCT on severe disruptive behavior [17, 20, 23]. Again, it can be speculated that even though SCT seems to impact negatively on the individuals social functioning, by making individuals more socially reluctant and less attentive to social cues , SCT also functions as a protective factor, making the individual more resilient to deviant behavior such as hostility [5, 23].
Another consequence of impaired social functioning associated with SCT might be seen in increased levels of peer-rejection. For example, teachers’ ratings of children on the item “cannot pay attention and looks sleepy” were related to greater peer rejections in pupils independent of internalizing, anxious or depressed features of the assessed child . The authors concluded that SCT was the only predictive factor with regard to peer rejection .
So far, no study focused on social perceptual functioning in children with SCT. Future studies should therefore implement the measurement of social cognitive as well as social perceptual performances of children with SCT in order to bridge the gap between SCT and social-perception as well as social-cognition. The observation that social deficits might arise due to slower responses or inattention to meaningful social cues might further plead for research assessing the timing sensitivity of children with SCT in social situations. In particular, considering that children with ADHD have a poorer perception of time [20, 58] and timing functions have been shown to be crucial in social interactions [59, 60], the examination of a relationship between abnormal timing functions and impaired social functioning in children with SCT could enhance the understanding of social shortcomings seen in SCT.
SCT treatment efficacy
Clinical observations suggested that treating children with ADHD/I and ADHD/C together might be detrimental for children with ADHD/I , underlining hereby the need for individualized treatments according to patients’ unique psychopathology. Similar, children with ADHD/I and SCT have been shown to benefit the most from treatment that addresses the processing deficits and social impairments associated with ADHD/I . For example, SCT symptoms were shown to be as responsive as ADHD/I symptoms to the Child Life and Attention Skill (CLAS) program devised by Pfiffner and colleagues . Furthermore, the positive effects remained stable at follow-up . The CLAS program was adapted from a program for the treatment of mild closed head injury in children and is characterized by prompts, routinization and task complexity reduction. Unfortunately, no control group was examined in this study so that it remains unclear to what amount the observed improvements of children were caused by nonspecific effects of treatment, such as the positive influence of the teacher or parent training. Ludwig and colleagues  showed that individuals with ADHD/I and SCT do not differ in their response to stimulant drug treatment using methylphenidate from individuals with ADHD/I without SCT. The CLAS program  might, therefore, be a promising approach to address symptoms seen in children with ADHD/I and SCT.
The current review’s aim was to provide a comprehensive overview of the psychometric as well as empirical validity of SCT, its etiology, its unique contribution to individuals’ neuro-cognitive profiles, its impact on individuals’ social and emotional well-being, as well as its treatment. Even though there seems to be no consensus yet whether SCT could account as a disorder itself [11, 16], recent studies confirm the link between ADHD/I and SCT [1, 10, 13, 23, 29, 36, 38].
The removal of SCT symptoms from the DSM-IV criteria of ADHD resulted in a loss of relevant information about cognitive impairments associated with ADHD/I  and might even lead to overdiagnosing of ADHD/C, in particular of those cases that would rather fit the category of ADHD/I and SCT or pure SCT . The fact that the items assessing SCT were not reintroduced into the current DSM-5 might increase ADHD’s homogeneity artificially [14, 26], leading thereby to a distorted diagnosis and treatment of individuals with ADHD.
Furthermore, SCT was present in or comorbid to a variety of clinical or physical disorders different from ADHD (e.g., clinical-referred children ; FAS ; leukemia survivors ), increasing the need for future research on SCT in a variety of clinical populations. The current review points out that it is warranted to assess for SCT symptoms in patients suffering from attention deficits within the context of neuro-cognitive treatment and rehabilitation.
However, before SCT can be used in research or clinical settings, its construct and empirical validity needs to be substantiated. Based on the research studies performed in the field of SCT, the current review concludes that SCT measures vary widely across studies and lack standardization. Three components of SCT (i.e., “slow”, “sleepy”, “daydreamer” ) however, seem promising for being implemented in future studies on SCT. By applying these unique SCT items, SCT emerged as a psychometrically valid factor which is even distinct from ADHD/I [2, 14]. Moreover, each of these three components was found to be independently related with different comorbidities . Accordingly, whereas the “slow” component was foremost related to ADHD/I, ADHD in general, and ODD, the other two components “sleepy/daydreamer” were more likely to be related to a more pure form of SCT . Even though some of the studies tried to integrate the individual impact of each of these three components of SCT [11, 13, 24], none of the studies explicitly assessed the items’ unique associations with ADHD subtypes or other comorbidities. The aim of future research could be to take the mentioned components as a starting point for further analysis of SCT and its behavioral as well as cognitive markers.
The majority of the reviewed studies were based on teacher and parent ratings. Self-measurements and objective measures of SCT (e.g., computerized cognitive tasks) are lacking so far, however, it was proposed that the nature of SCT symptoms requires longer behavioral as well as cognitive observations. Simple observations of ten minutes of on-task behavior were, for example, considered to be insufficient to reasonably capture SCT .
Whereas a link between sustained attention deficits and SCT was consistently found , the hypothesized association of SCT with both cognitive and behavioral speed [19, 58] or slowed information processing in general [12, 14, 17] was rather inconsistent and needs further investigation. It has been hypothesized that a decreased processing speed might lead to a general distortion in individuals’ perception of time  and impacts on several timing functions such as motor- and perceptual timing, as well as temporal foresight . These timing functions, however, are important for motor control, decision making and the individual’s psychological orientation in time . Several studies so far showed that patients with ADHD present with a different sense of time [58, 65, 66], see  for a recent review. Given SCT’s strong link to ADHD and its proposed association with slowed processing speed, it would be interesting to examine the impact of SCT on timing functions in general and perceptual timing in particular.
The findings concerning the impact of SCT on classroom behavior and children’s academic achievement remain inconsistent [10, 36], however, SCT’s impact on children’s social- as well as emotional well-being has been shown to be concerning [5, 37, 51], with SCT showing a clear link to internalizing disorders such as anxiety and depression [2, 8, 11, 13, 37].
While the majority of studies focused on adolescents or children, only one study examined SCT in adulthood . Because of the clear association between ADHD and SCT and the fact that ADHD persists from childhood throughout adulthood , thorough examinations of SCT in longitudinal studies would be desirable. These studies could, for instance, provide information about the presence and consequences of SCT in community-based as well as clinical populations and add valuable insights into the developmental trajectory of SCT.
The only genetic study available in this field indicates that SCT seems to share some of the genes with ADHD but is most strongly associated with environmental factors . The idea, that SCT is a by-product of ADHD related environmental factors  seems worth to be further studied in future research. Based on Barkley’s  classification of SCT symptoms, it can be assumed that if a threshold of 5 or more out of 9 SCT symptoms will be applied as a standard for diagnosing SCT, 5.1% of the general population would be diagnosed with SCT, which is comparable to the number of ADHD diagnoses in children . Barkley’s estimate therefore gives an impression of the number of patients which can be expected if SCT establishes as a disorder itself.
Based on the discussed literature, it can be concluded that SCT in ADHD but also SCT in other populations and pathologies is understudied. Whereas first attempts for valid and consistent measurements have been made , recent studies on SCT lack coherence and standardization of measurement. To allow the diagnosis of SCT, a consensus about which dimensions actually represent SCT has to be reached first. Two factors, represented by the condition “sleepy/daydreamer” seem promising for a future taxonomy of SCT . Neurocognitive tests focusing on timing functions and attention (in particular sustained attention) should be combined with behavioral observations that target sleepy/daydreaming behavior and absent-mindedness, without missing the importance of assessing SCT’s link to internalizing and other mood disorders. Especially, patients with depressive disorders or acquired brain lesions (e.g. during the phase of neuro-rehabilitation) might benefit from a thorough assessment of comorbid SCT. SCT symptoms have been shown to improve by means of non-pharmacological treatment . As these results are rather preliminary, additional psycho-educative, therapeutic, and behavioral interventions should be tested for their efficacy in populations with clinical levels of SCT. Studies on the genetic background of SCT should be encouraged, testing hereby the assumption whether SCT is a by-product elicited by the environmental constraints put forward by the disorder to which SCT is comorbid to (e.g., ADHD).
Lee S, Burns GL, Snell J, McBurnett K: Validity of the sluggish cognitive tempo symptom dimension in children: Sluggish cognitive tempo and adhd-inattention as distinct symptom dimensions. J Abnorm Child Psychol 2013,42(1):7–19. doi:10.1007/s10802–013–9714–3
Penny AM, Waschbusch DA, Klein RM, Corkum P, Eskes G: Developing a measure of sluggish cognitive tempo for children: content validity, factor structure, and reliability. Psychol Assess 2009, 21: 380–389. doi:10.1037/a0016600
Graham DM, Crocker N, Deweese BN, Roesch SC, Coles CD, Kable JA, Mattson SN: Prenatal alcohol exposure, attention‒deficit/hyperactivity disorder, and sluggish cognitive tempo. Alcohol Clin Exp Res 2013, 37: E338-E346.
Reeves CB, Palmer S, Gross AM, Simonian SJ, Taylor L, Willingham E, Mulhern RK: Brief report: sluggish cognitive tempo among pediatric survivors of acute lymphoblastic leukemia. J Pediatr Psychol 2007,32(9):1050–1054. doi:10.1093/jpepsy/jsm063
Becker SP, Luebbe AM, Fite PJ, Stoppelbein L, Greening L: Sluggish cognitive tempo in psychiatrically hospitalized children: Factor structure and relations to internalizing symptoms, social problems, and observed behavioral dysregulation. J Abnorm Child Psychol 2013,42(1):49–62. doi:10.1007/s10802–013–9719-y
Milich R, Balentine AC, Lynam DR: ADHD combined type and ADHD predominantly inattentive type are distinct and unrelated disorders. Clin Psychol Sci Pract 2001,8(4):463–488. doi:10.1093/clipsy/8.4.463
American Psychiatric Association: Diagnostic and statistical manual of mental disorders (DSM-IV).. Washington (DC): American Psychiatric Association; 1994.
Schatz DB, Rostain AL: ADHD with comorbid anxiety: a review of the current literature. J Atten Disord 2006,10(2):141–149. doi:10.1177/1087054706286698
Frick PJ, Lahey BB, Applegate B, Kerdyck L, Ollendick T, Hynd GW, Waldman I: DSM-IV field trials for the disruptive behavior disorders: symptom utility estimates. J Am Acad Child Adolesc Psychiatr 1994,33(4):529–539. doi:10.1097/00004583–199405000–00011
Langberg JM, Becker SP, Dvorsky MR: The association between sluggish cognitive tempo and academic functioning in youth with attention-deficit/hyperactivity disorder (ADHD). J Abnorm Child Psychol 2013,42(1):91–103. doi:10.1007/s10802–013–9722–3
Bauermeister JJ, Barkley RA, Bauermeister JA, Martínez JV, McBurnett K: Validity of the sluggish cognitive tempo, inattention, and hyperactivity symptom dimensions: Neuropsychological and psychosocial correlates. J Abnorm Child Psychol 2012,40(5):683–697. doi:10.1007/s10802–011–9602–7
Bauermeister JJ, Matos M, Reina G, Salas CC, Martínez JV, Cumba E, Barkley RA: Comparison of the DSM-IV combined and inattentive types of ADHD in a school-based sample of Latino/Hispanic children. J Child Psychol Psychiatr 2005,46(2):166–179. doi:10.1111/j.1469–7610.2004.00343.x
Garner AA, Marceaux JC, Mrug S, Patterson C, Hodgens B: Dimensions and correlates of attention deficit/hyperactivity disorder and sluggish cognitive tempo. J Abnorm Child Psychol 2010,38(8):1097–1107. doi:10.1007/s10802–010–9436–8
Hartman CA, Willcutt EG, Rhee SH, Pennington BF: The relation between sluggish cognitive tempo and DSM-IV ADHD. J Abnorm Child Psychol 2004,32(5):491–503. doi:10.1023/B:JACP.0000037779.85211.29
Barkley RA, DuPaul GJ, McMurray MB: Comprehensive evaluation of attention deficit disorder with and without hyperactivity as defined by research criteria. J Consult Clin Psychol 1990,58(6):775–789. doi:10.1037/0022–006X.58.6.775
Barkley RA: Distinguishing sluggish cognitive tempo from attention-deficit/hyperactivity disorder in adults. J Abnorm Psychol 2012,121(4):978–990. doi:10.1037/a0023961
Carlson CL, Mann M: Sluggish cognitive tempo predicts a different pattern of impairment in the attention deficit hyperactivity disorder, predominantly inattentive type. J Clin Child Adolesc Psychol 2002,31(1):123–129. doi:10.1207/153744202753441738
Diamond A: Attention-deficit disorder (attention-deficit/hyperactivity disorder without hyperactivity): A neurobiologically and behaviorally distinct disorder from attention-deficit/hyperactivity disorder (with hyperactivity). Dev Psychopathol 2005,17(3):807–825. doi:10.1017/S0954579405050388
McBurnett K, Pfiffner LJ, Frick PJ: Symptom properties as a function of ADHD type: an argument for continued study of sluggish cognitive tempo. J Abnorm Child Psychol 2001,29(3):207–213. doi:10.1023/A:1010377530749
Barkley RA: Attention-Deficit/Hyperactivity disorder. Edited by: Wolfe DA, Mash EJ. New York, NY USA: Guilford Publications; 2006:91–152.
Froehlich TE, Lanphear BP, Epstein JN, Barbaresi WJ, Katusic SK, Kahn RS: Prevalence, recognition, and treatment of attention-deficit/hyperactivity disorder in a national sample of US children. Arch Pediatr Adolesc Med 2007, 161: 857–864.
Merikangas KR, He J, Brody D, Fisher PW, Bourdon K, Koretz DS: Prevalence and treatment of mental disorders among US children in the 2001–2004 NHANES. Pediatrics 2010,125(1):75–81. doi:10.1542/peds.2008–2598
Mikami AY, Huang-Pollock C, Pfiffner LJ, McBurnett K, Hangai D: Social skills differences among attention-deficit/hyperactivity disorder types in a chat room assessment task. J Abnorm Child Psychol 2007,35(4):509–521. doi:10.1007/s10802–007–9108–5
Wåhlstedt C, Bohlin G: DSM-IV-defined inattention and sluggish cognitive tempo: Independent and interactive relations to neuropsychological factors and comorbidity. Child Neuropsychol 2010,16(4):350–365. doi:10.1080/09297041003671176
Becker SP: Topical review: Sluggish cognitive tempo: Research findings and relevance for pediatric psychology. J Pediatr Psychol 2013,38(10):1051–1057. doi:10.1093/jpepsy/jst058
Moruzzi S, Rijsdijk F, Battaglia M: A twin study of the relationships among inattention, hyperactivity/impulsivity and sluggish cognitive tempo problems. J Abnorm Child Psychol 2013,42(1):63–75. doi:10.1007/s10802–013–9725–0
Harrington KM, Waldman ID: Evaluating the utility of sluggish cognitive tempo in discriminating among DSM-IV ADHD subtypes. J Abnorm Child Psychol 2010,38(2):173–184. doi:10.1007/s10802–009–9355–8
Lahey BB, Schaughency EA, Hynd GW, Carlson CL, Nieves N: Attention deficit disorder with and without hyperactivity: Comparison of behavioral characteristics of clinic-referred children. J Am Acad Child Adolesc Psychiatr 1987,26(5):718–723. doi:10.1097/00004583–198709000–00017
Skansgaard EP, Burns GL: Comparison of DSM-IV ADHD combined and predominantly inattention types. Child Fam Behav Ther 1998,20(1):1–14. doi:10.1300/J019v20n01_01
Todd RD, Rasmussen ER, Wood C, Levy F, Hay DA: Should sluggish cognitive tempo symptoms be included in the diagnosis of attention-deficit/hyperactivity disorder? J Am Acad Child Adolesc Psychiatr 2004,43(5):588–597. doi:10.1097/00004583–200405000–00012
Solanto MV, Gilbert SN, Raj A, Zhu J, Pope-Boyd S, Stepak B, Newcorn JH: Neurocognitive functioning in AD/HD, predominantly inattentive and combined subtypes. J Abnorm Child Psychol 2008,36(1):729–744. doi:10.1007/s10802–007–9170-z
Pfiffner LJ, Mikami AY, Huang-Pollock C, Easterlin B, Zalecki C, McBurnett K: A randomized, controlled trial of integrated home-school behavioral treatment for ADHD, predominantly inattentive type. J Am Acad Child Adolesc Psychiatr 2007,46(8):1041–1050. doi:10.1097/chi.0b013e318064675f
Skirbekk B, Hansen BH, Oerbeck B, Kristensen H: The relationship between sluggish cognitive tempo, subtypes of attention-deficit/hyperactivity disorder, and anxiety disorders. J Abnorm Child Psychol 2011,39(4):513–525. doi:10.1007/s10802–011–9488–4
Hinshaw SP: Preadolescent girls with attention-deficit/hyperactivity disorder: I. background characteristics, comorbidity, cognitive and social functioning, and parenting practices. J Consult Clin Psychol 2002,70(5):1086–1098. doi:10.1037/0022–006X.70.5.1086
Achenbach TM: Integrative guide for the 1991 CBCL/4–18, YSR & TRF Profiles. Burlington, VT: University of Vermont Department of Psychiatry; 1991.
Jacobson LA, Murphy-Bowman S, Pritchard AE, Tart-Zelvin A, Zabel TA, Mahone EM: Factor structure of a sluggish cognitive tempo scale in clinically-referred children. J Abnorm Child Psychol 2012,40(8):1327–1337. doi:10.1007/s10802–012–9643–6
Becker SP, Langberg JM: Attention-deficit/hyperactivity disorder and sluggish cognitive tempo dimensions in relation to executive functioning in adolescents with ADHD. Child Psychiatry Hum Dev 2013,45(1):1–11. doi:10.1007/s10578–013–0372-z
Desman C, Petermann F, Hampel P: Deficit in response inhibition in children with attention deficit/hyperactivity disorder (ADHD): Impact of motivation? Child Neuropsychol 2008,14(6):483–503. doi:10.1080/09297040701625831
Faraone SV, Perlis RH, Doyle AE, Smoller JW, Goralnick JJ, Holmgren MA, Sklar P: Molecular genetics of attention-Deficit/Hyperactivity disorder. Biol Psychiatry 2005,57(11):1313–1323. doi:10.1016/j.biopsych.2004.11.024
Conners CK: The Conners’ Continuous Performance Test. Toronto: Multi-Health Systems; 1994.
Huang-Pollock C, Nigg JT, Carr TH: Deficient attention is hard to find: Applying the perceptual load model of selective attention to attention deficit hyperactivity disorder subtypes. J Child Psychol Psychiatr 2005,46(11):1211–1218. doi:10.1111/j.1469–7610.2005.00410.x
Tucha O, Walitza S, Mecklinger L, Sontag TA, Kübber S, Linder M, Lange KW: Attentional functioning in children with ADHD-predominantly hyperactive-impulsive type and children with ADHD-combined type. J Neural Transm 2006, 113: 1943–1953. doi:10.1007/s00702–006–0496–4
Tucha L, Tucha O, Laufkötter R, Walitza S, Klein HE, Lange KW: Neuropsychological assessment of attention in adults with different subtypes of attention deficit hyperactivity disorder. J Neural Transm 2008, 115: 269–278. doi:10.1007/s00702–007–0836-z
Lahey BB, Neeper R, Frick PJ: Manual for the Comprehensive Behavior Rating Scale for Children (CBRSC). San Antonio, TX: Psychological Corporation; 1990.
Anderson P: Assessment and development of executive function (EF) during childhood. Child Neuropsychol 2002,8(2):71–82. doi:10.1076/chin.22.214.171.12424
Barkley RA, Fischer M: Predicting impairment in major life activities and occupational functioning in hyperactive children as adults: Self-reported executive function (EF) deficits versus EF tests. Dev Neuropsychol 2011,36(2):137–161. doi:10.1080/87565641.2010.549877
Brooks N, Campsie L, Symington C, Beattie A: The effects of severe head injury on patient and relative within seven years of injury. J Head Trauma Rehabil 1987,2(3):1–13. doi:10.1097/00001199–198709000–00003
van Zomeren AH, van den Burg W: Residual complaints of patients two years after severe head injury. J Neurol Neurosurg Psychiatry 1985,48(1):21–28. doi:10.1136/jnnp.48.1.21
Schaughency EA, Vannatta K, Langhinrichsen J, Lally CM, Seeley J: Correlates of sociometric status in school children in buenos aires. J Abnorm Child Psychol 1992,20(3):317–326. doi:10.1007/BF00916695
McConaughy SH, Ivanova MY, Antshel K, Eiraldi RB, Dumenci L: Standardized observational assessment of attention deficit hyperactivity disorder combined and predominantly inattentive subtypes: II. Classroom observations. Sch Psychol Rev 2009,38(3):362–381. doi:10.1080/15374416.2010.501287
Marshall SA, Evans SW, Eiraldi RB, Becker SP, Power TJ: Social and Academic Impairment in Youth with ADHD, Predominately Inattentive Type and Sluggish Cognitive Tempo. Germany: Springer; 2013. doi:10.1007/s10802–013–9758–4
American Psychiatric Association: Diagnostic and Statistical Manual of Mental Disorders - Text Revision. Washington DC: The American Psychiatric Association; 2000.
Gaub M, Carlson CL: Gender differences in ADHD: A meta-analysis and critical review. J Am Acad Child Adolesc Psychiatr 1997,36(8):1036–1045.
Greene RW, Biederman J, Faraone SV, Sienna M, Garcia-Jetton J: Adolescent outcome of boys with attention-deficit/hyperactivity disorder and social disability: Results from a 4-year longitudinal follow-up study. J Consult Clin Psychol 1997,65(5):758–767. doi:10.1037/0022–006X.65.5.758
Greene RW, Biederman J, Faraone SV, Monuteaux MC, Mick E, DuPre EP, Goring JG: Social impairment in girls with ADHD: Patterns, gender comparisons, and correlates. J Am Acad Child Adolesc Psychiatr 2001,40(6):704–710. doi:10.1097/00004583–200106000–00016
Nijmeijer JS, Minderaa RB, Buitelaar JK, Mulligan A, Hartman CA, Hoekstra PJ: Attention-deficit/hyperactivity disorder and social dysfunctioning. Clin Psychol Rev 2008,28(4):692–708. doi:10.1016/j.cpr.2007.10.003
Bagwell CL, Molina BSG, Pelham WE, Hoza B: Attention-deficit hyperactivity disorder and problems in peer relations: Predictions from childhood to adolescence. J Am Acad Child Adolesc Psychiatr 2001,40(11):1285–1292. doi:10.1097/00004583–200111000–00008
Barkley RA, Koplowitz S, Anderson T, McMurray MB: Sense of time in children: with ADHD Effects of duration, distraction, and stimulant medication. J Int Neuropsychol Soc 1997, 3: 359–369.
Reed CL, McGoldrick JE: Action during body perception: Processing time affects self-other correspondences. Soc Neurosci 2007,2(2):134–149. doi:10.1080/17470910701376811
Trevarthen C, Aitken KJ: Infant intersubjectivity: Research, theory, and clinical applications. J Child Psychol Psychiatr 2001,42(1):3–48. doi:10.1111/1469–7610.00701
Antshel KM, Remer R: Social skills training in children with attention deficit hyperactivity disorder: A randomized-controlled clinical trial. J Clin Child Adolesc Psychol 2003,32(1):153–165. doi:10.1207/15374420360533149
Ludwig HT, Matte B, Katz B, Rohde LA: Do sluggish cognitive tempo symptoms predict response to methylphenidate in patients with attention-deficit/hyperactivity disorder–inattentive type? J Child Adolesc Psychopharmacol 2009,19(4):461–465. doi:10.1089/cap.2008.0115
Noreika V, Falter CM, Rubia K: Timing deficits in attention-deficit/hyperactivity disorder (adhd): Evidence from neurocognitive and neuroimaging studies. Neuropsychologia 2012,51(2):235–266. doi:10.1016/j.neuropsychologia.2012.09.036
Buhusi CV, Meck WH: What makes us tick? Functional and neural mechanisms of interval timing. Nat Rev Neurosci 2005,6(10):755–765. doi:10.1038/nrn1764
Toplak ME, Dockstader C, Tannock R: Temporal information processing in ADHD: findings to date and new methods. J Neurosci Methods 2006, 151: 15–29. doi:10.1016/j.jneumeth.2005.09.018
Toplak ME, Rucklidge JJ, Hetherington R, John SCF, Tannock R: Time perception deficits in attention-deficit/hyperactivity disorder and comorbid reading difficulties in child and adolescent samples. J Child Psychol Psychiatr 2003,44(6):888–903. doi:10.1111/1469–7610.00173
Simon V, Czobor P, Bálint S, Mészáros A, Bitter I: Prevalence and correlates of adult attention-deficit hyperactivity disorder: Meta-analysis. Br J Psychiatry 2009,194(3):204–221. doi:10.1192/bjp.bp.107.048827
Puig-Antich J, Chambers W: The Schedule for Affective Disorders and Schizophrenia for School-aged Children. New York: New York State Psychiatric Institute; 1987.
Conners CK: Rating scales for use in drug studies with children. Psychopharmacol Bull 1973, 41: 24–84. [Special Issue on Children]
Quay HC, Peterson DR: Interim Manual for the Revised Behavior Problem Checklist. Coral Gables. Florida: University of Miami; 1983.
Coie JD, Dodge KA, Coppotelli H: ‘Dimensions and types of social status: A cross-age perspective’: Correction. Dev Psychol 1983,19(2):341–362. doi:10.1037/0012–16126.96.36.199
Burns GL, Walsh JA, Owen SM, Snell J: Internal validity of attention deficit hyperactivity disorder, oppositional defiant disorder, and overt conduct disorder symptoms in young children: Implications from teacher ratings for a dimensional approach to symptom validity. J Clin Child Psychol 1997,26(3):266–275. doi:10.1207/s15374424jccp2603_5
Achenbach TM: The direct observation form of the child behavior checklist (revised). Burlington: University of Vermont; 1986.
Swanson JM: School-based assessments and interventions for ADD students. Irvine, CA: KC Publishing; 1992.
Dishion T: Peer context of troublesome child and adolescent behavior. In Understanding troubled and troublesome youth. Edited by: Leone PE. Newbury Park, CA: Sage; 1990:128–153.
Weiler MD, Bernstein JH, Bellinger D, Waber DP: Information processing deficits in children with attention-deficit/hyperactivity disorder, inattentive type, and children with reading disability. J Learn Disabil 2002,35(5):448–461. doi:10.1177/00222194020350050501
Kaufman A, Kaufman N: Kaufman brief intelligence test. Circle Pines, MN: American Guidance Service; 1990.
Waber DP, Weiler MD, Bellinger DC, Marcus DJ, Forbes PW, Wypij D, Wolff PH: Diminished motor timing control in children referred for diagnosis of learning problems. Dev Neuropsychol 2000,17(2):181–197. doi:10.1207/S15326942DN1702_03
Barkley RA, Murphy KR: Attention-deficit Hyperactivity Disorder: A Clinical Workbook. 2nd edition. New York, NY USA: Guilford Press; 1998.
Reich W, Welner Z: Revised version of the Diagnostic Interview for children and adolescents (DICA-R). St. Louis, MO: Washington University School of Medicine, Department of Psychiatry; 1988.
Wechsler D: Examiner’s manual: Wechsler Intelligence Scale for children—revised. New York: The Psychological Corporation; 1974.
Wechsler D: Manual for the Wechsler Adult Intelligence Scale—Revised. San Antonio: The Psychological Corporation; 1981.
Dunn LM, Markwardt FC: Examiner’s manual: Peabody Individual Achievement Test. Circle Pines, MN: American Guidance Service; 1970.
Bauermeister JJ: Desarrollo y utilizacio’n del Inventario de Comportamiento-Escuela (IDC-E) en la evaluacion de ninõs puertorriquenõs. San Juan, PR: Atención, Inc.; 1994.
Shaffer D, Fisher P, Lucas CP, Dulcan MK, Schwab-Stone M: NIMH diagnostic interview schedule for children version IV (NIMH DISC-IV): Description, differences from previous versions, and reliability of some common diagnoses. J Am Acad Child Adolesc Psychiatr 2000,39(1):28–38. doi:10.1097/00004583–200001000–00014
Bird HR, Canino GJ, Rubio-Stipec M, Ribera JC: Further measures of the psychometric properties of the children's global assessment scale. Arch Gen Psychiatry 1987,44(9):821–824. doi:10.1001/archpsyc.1987.01800210069011
Gresham F, Elliott S: Social skills rating system. Circle Pines: American Guidance Service; 1990.
Herrans LL, Rodríguez JM: Manual EIWN-R de Puerto Rico [WISC-R Puerto Rico manual]. San Antonio: The Psychological Corporation; 1992.
Hammill DD, Larsen SC, Wiederholt JL, Fountain- Chambers JF: Prueba de Lectura y Lenguaje Escrito. Austin, TX: PROED; 1982.
Koppitz EM: Bender gestalt test: Visual aural digit span test and reading achievement. J Learn Disabil 1975,8(3):154–157. doi:10.1177/002221947500800308
Conners CK: Conners’ Continuous Performance Test computer program: User’s manual. Toronto, Ontario, Canada: Multi-Health Systems; 1995.
Ambulatory Monitoring Inc: Mini Motion Logger Actigraph User’s Guide for Act: Operational Software. New York: ; 1995.
Bernal G, Bonilla J, Santiago E: Psychometric properties of the BDI and SCL-36 in a Puerto Rican sample. Am J Psychol 1995, 27: 207–230.
Goodman SH, Hoven CW, Narrow WE, Cohen P, Fielding B, Alegria M, Dulcan MK: Measurement of risk for mental disorders and competence in a psychiatric epidemiologic community survey: The national institute of mental health methods for the epidemiology of child and adolescent mental disorders (MECA) study. Soc Psychiatry 1998,33(4):162–173. doi:10.1007/s001270050039
Bauermeister JJ, Matos M, Reina G: Do ADHD and ADD have similar impacts on family life? ADHD Rep 1999, 7: 8–9.
Salas-Serrano CC Dissertation Abstracts International. In La crianza de los niños y las niñas con el trastorno por de’ficit de atencio’n e hiperactividad y su entorno familiar y social [The parenting of children with ADHD and their social and family environment]. Doctoral dissertation, Volume 64. Rio Piedras: University of Puerto Rico; 2001:1505.
Reynolds C, Kamphaus R: Behavior Assessment System for Children: Manual. MN: American Guidance Service, Inc.; 1992.
DuPaul GJ, Power TJ, Anastopoulos AD, Reid R: ADHD rating Scale—IV: Checklists, norms, and clinical interpretation. New York, NY USA: Guilford Press; 1998.
Conners K: Conners’ Rating Scales–Revised Technical Manual. New York: Multi Health Systems; 1997.
Maylor EA, Lavie N: The influence of perceptual load on age differences in selective attention. Psychol Aging 1998,13(4):563–573. doi:10.1037/0882–79188.8.131.523
Huang-Pollock CL, Carr TH, Nigg JT: Perceptual load influences late versus early selection in child and adult selective attention. Dev Psychol 2002, 38: 363–375.
Wechsler D: Wechsler intelligence scale for children-third edition; WISC-III. Manual. Norwegian Manual Supplement 2003 (Pearson Assessment). San Antonio: The Psychological Corporation; 1991.
Taylor LB: Localization of cerebral lesions by psychological testing. Clin Neurosurg 1969, 16: 269–287.
Rourke BP, Gates RD: The Underlining Test (preliminary norms). Windsor, Ontario, Canada: Department of Psychology, University of Windsor; 1980.
Rourke BP, Orr R: Prediction of the reading and spelling performances of normal and retarded readers: A four-year follow-up. J Abnorm Child Psychol 1977, 5: 9–20.
Wechsler D: Manual for the Wechsler intelligence scale for children- fourth edition (WISC-IV). NewYork: Psychological Corporation/Harcourt Brace; 2003.
Wechsler D: Wechsler abbreviated scale of intelligence; WASI. Manual. Norwegian Manual Supplement 2007 (Pearson Assessment). San Antonio: The Psychological Corporation; 1999.
Wechsler D: Wechsler individual achievement test- Second Edition (WIAT-II). New York: Psychological Corporation/Harcourt Brace; 2001.
McBurnett K, Pfiffner LJ: Sluggish Cognitive Tempo (SCT Scale). San Francisco: University of California; 2005.
Gadow KD, Sprafkin J: Child Symptom Inventories Manual. Stony Brook, NY: Checkmate Plus; 1994.
Abikoff H, Gallagher R: Children’s Organizational Skills Scale. New York: Multi-Health Systems; 2003.
Pfiffner LJ, Mikami A: Child Life Skills Scale. UCSF; 2005. Available at email@example.com
NIMH: Clinical Global Impression Scale (CGI). Psychopharmacol Bull 1985, 21: 839–843.
Wechsler D: Weschsler Adult Intelligence Scale-III. San Antonio, TX: The Psychological Corporation; 1997.
The Psychological Corporation: The Wechsler individual achievement test. New York: Harcourt, Brace, Jovanovich; 1992.
Swanson JM, Sandman CA, Deutsch C, Baren M: Methylphenidate (Ritalin) given with or before breakfast, Part I: behavioral, cognitive, and electrophysiological effects. Pediatrics 1983, 72: 49–55.
Sonuga-Barke E, Taylor E, Sembi S, Smith J: Hyperactivity and delay aversion: I. the effect of delay on choice. J Child Psychol Psychiatr 1992,33(2):387–398. doi:10.1111/j.1469–7610.1992.tb00874.x
Buschke H, Fuld PA: Evaluating storage, retention, and retrieval in disordered memory and learning. Neurology 1974,24(11):1019–1025.
Sheslow D, Adams W: Wide range assessment of memory and learning. Wilmington, DE: Jastak; 1990.
Sternberg S: The discovery of processing stages: Extensions of donders’ method. Acta Psychol Amsterdam 1969, 30: 276–315. doi:10.1016/0001–6918(69)90055–9
Golden CJ: Stroop Color and Word Test: A Manual for Clinical and Experimental Use. Chicago: Stoelting; 1978.
Posner MI, Petersen SE: The attention system of the human brain. Annu Rev Neurosci 1990, 13: 25–42. doi:10.1146/annurev.ne.13.030190.000325
Culbertson WC, Zillmer EA: The tower of London [sub] DX [/sub]: a standardized approach to assessing executive functioning in children. Arch Clin Neuropsychol 1998,13(3):285–301. doi:10.1016/S0887–6177(97)00033–4
Berg EA: A simple objective technique for measuring flexibility in thinking. J Gen Psychol 1948, 39: 15–22. doi:10.1080/00221309.1948.9918159
Klasen H, Woerner W, Wolke D, Meyer R, Overmeyer S, Kaschnitz W, Goodman R: Comparing the german versions of the strengths and difficulties questionnaire (SDQ-deu) and the child behavior checklist. Eur Child Adolesc Psychiatry 2000,9(4):271–276. doi:10.1007/s007870070030
Zimmermann P, Fimm B Handbook – Part 1. In Test Battery for Attentional Performance (TAP). Würselen: Psytest; 1993. German
Zimmermann P, Fimm B Handbook –Part 2. In Test Battery for Attentional Performance (TAP). Würselen: Psytest; 1994. German
Polanczyk GV, Eizirik M, Aranovich V, Denardin D, da Silva TL, da Conceição TV, Rohde LA: Concordância entre observadores da entrevista semi-estruturada para diagnóstico em psiquiatria da infância, versão epidemiológica (K-SADS-E). Rev Bras Psiquiatr 2003,25(2):87–90. doi:10.1590/S1516–44462003000200007
Rohde LA, Szobot C, Polanczyk G, Schmitz M, Martins S, Tramontina S: Attention-Deficit/Hyperactivity disorder in a diverse culture: Do research and clinical findings support the notion of a cultural construct for the disorder? Biol Psychiatry 2005,57(11):1436–1441. doi:10.1016/j.biopsych.2005.01.042
Swanson JM, Kraemer HC, Hinshaw SP, Arnold LE, Conners CK, Abikoff HB, Wu M: Clinical relevance of the primary findings of the MTA: Success rates based on severity of ADHD and ODD symptoms at the end of treatment. J Am Acad Child Adolesc Psychiatr 2001,40(2):168–179. doi:10.1097/00004583–200102000–00011
Pelham WE, Gnagy EM, Greenslade KE, Milich R: Teacher ratings of DSM-III—R symptoms for the disruptive behavior disorders. J Am Acad Child Adolesc Psychiatr 1992,31(2):210–218.
Jellinek MS: Pediatric symptom checklist: screening school-age children for psychosocial dysfunction. J Pediatr 1988, 112: 201–209.
Berlin L, Bohlin G: Response inhibition, hyperactivity, and conduct problems among preschool children. J Clin Child Adolesc Psychol 2002,31(2):242–251. doi:10.1207/153744202753604511
Gerstadt CL, Hong YJ, Diamond A: The relationship between cognition and action: Performance of children 31/2–7 years old on a Stroop-like day-night test. Cognition 1994, 53: 129–153.
McInerney RJ, Hrabok M, Kerns KA: The children's size-ordering task: a new measure of nonverbal working memory. J Clin Exp Neuropsychol 2005,27(6):735–745. doi:10.1081/13803390490918633
Nigg JT: What causes ADHD? Understanding what goes wrong and why. New York, NY USA: Guilford Press; 2006.
van der Meere J, Sergeant J: Controlled processing and vigilance in hyperactivity: time will tell. J Abnorm Child Psychol 1988,16(6):641–655. doi:10.1007/BF00913475
Wilding J: Is attention impaired in ADHD? Br J Dev Psychol 2005,23(4):487–505. doi:10.1348/026151005X48972
Malmberg M, Rydell A, Smedje H: Validity of the swedish version of the strengths and difficulties questionnaire (SDQ-swe). Nord J Psychiatry 2003,57(5):357–363. doi:10.1080/08039480310002697
Shaffer D, Gould MS, Brasic J, Ambrosini PJ, Fischer P, Bird H, Aluwahlia S: A children’s global assessment scale (CGAS). Arch Gen Psychiatry 1983,40(11):1228–1231.
Barkley RA, Murphy KR: Attention-deficit hyperactivity disorder: a clinical workbook. New York: Guilford; 1998.
Rueda MR, Fan J, McCandliss BD, Halparin JD, Gruber DB, Lercari LP, Posner MI: Development of attentional networks in childhood. Neuropsychologia 2004,42(8):1029–1040. doi:10.1016/j.neuropsychologia.2003.12.012
Barkley RA: The Barkley Adult ADHD Rating Scale–IV. New York, NY: Guilford Press; 2011.
Barkley RA: The Barkley Functional Impairment Scale. New York, NY: Guilford Press; 2011.
Barkley RA: The Barkley Deficits in Executive Functioning Scale. New York, NY: Guilford Press; 2011.
Kaufman AS, Kaufman NL: K-ABC interpretive manual. Circle Pines: American Guidance Service; 1983.
Barkley RA, Edwards G, Laneri M, Fletcher K, Metevia L: Executive functioning, temporal discounting, and sense of time in adolescents with attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD). J Abnorm Child Psychol 2001,29(6):541–556. doi:10.1023/A:1012233310098
Barkley RA, Du Paul GJ, McMurray MB: Attention deficit disorder with and without hyperactivity: Clinical response to three dose levels of methylphenidate. Pediatrics 1991, 87: 519–531.
Newby R: The wisconsin selective reminding test. Milwaukee, WI: Author; 1989.
Denckla MB, Rudel R: Rapid ‘automatized’ naming of pictured objects, colors, letters and numbers by normal children. Cortex 1974,10(2):186–202.
Woodcock RW: Batería woodcock psicoeducativa en Español [woodcock Spanish psycho-educational battery]. Allen: DLM Teaching Resources; 1982.
Waldman ID, Rowe DC, Abramowitz A, Kozel ST, Mohr JH, Sherman SL, Cleveland HH, Sanders ML, Gard JMC, Stever C: Association and linkage of the dopamine transporter gene and attention-deficit hyperactivity disorder in children. Am J Hum Genet 1998, 63: 1767–1776.
Wolraich ML, Feurer ID, Hannah JN, Baumgaertel A, Pinnock TY: Obtaining systematic teacher reports of disruptive behavior disorders utilizing DSM-IV. J Abnorm Child Psychol 1998,26(2):141–152. doi:10.1023/A:1022673906401
Fabiano GA, Pelham WE, Waschbusch DA, Gnagy EM, Lahey BB, Chronis AM, Burrows-Maclean L: A practical measure of impairment: psychometric properties of the impairment rating scale in samples of children with attention deficit hyperactivity disorder and two school-based samples. J Clin Child Adolesc Psychol 2006,35(3):369–385. doi:10.1207/s15374424jccp3503_3
Achenbach TM, Rescorla LA: Manual for the ASEBA School-age Forms and Profiles. Burlington: University of Vermont; 2001. Achenbach, T. M. (1991a). Manual for the child behavior checklist/4- 18, and 1991 profile. Burlington: University of Vermont Department of Psychiatry
Derogatis LR: The hopkins symptom checklist (HSCL): a self-report symptom inventory. Behav Sci 1974,19(1):1–15. doi:10.1002/bs.3830190102
Gioia GA, Isquith PK, Guy SC, Kenworthy L: Test review: behavior rating inventory of executive function. Child Neuropsychol 2000, 6: 235–238.
Jones KL, Robinson LK, Bakhireva LN, Marintcheva G, Storojev V, Strahova A, Sergeevskaya S, Budantseva S, Mattson SN, Riley EP, Chambers CD: Accuracy of the diagnosis of physical features of fetal alcohol syndrome by pediatricians after specialized training. Pediatrics 2006, 118: e1734-e1738.
Mattson SN, Foroud T, Sowell ER, Jones KL, Coles CD, Fagerlund A, Autti-Rämö I, May PA, Adnams CM, Konovalova V, Wetherill L, Arenson AD, Barnett WK, Riley EP: The CIFASD: Collaborative Initiative on Fetal Alcohol Spectrum Disorders: methodology of clinical projects. Alcohol 2010, 44: 635–641.
Anesko KM, Schoiock G, Ramirez R, Levine FM: The homework problem checklist: assessing children’s homework difficulties. Behav Assess 1987,9(2):179–185.
Burns GL, Lee S: Child and Adolescent Disruptive Behavior Inventory–Teacher Version 5.0. Pullman, WA: Author; 2010.
Achenbach TM, Becker A, Döpfner M, Heiervang E, Roessner V, Steinhausen H, Rothenberger A: Multicultural assessment of child and adolescent psychopathology with ASEBA and SDQ instruments: Research findings, applications, and future directions. J Child Psychol Psychiatr 2008,49(3):251–275. doi:10.1111/j.1469–7610.2007.01867.x
The authors declare that they have no competing interests.
All authors contributed to the design and analysis of the review. AKM and LT drafted the manuscript. All authors critically revised the manuscript. All authors read and approved the final manuscript.