Executive functioning and olfactory identification in young adults with attention deficit-hyperactivity disorder

Relationship of the Wender Utah Rating Scale to objective measures of attention

The Wender Utah Rating Scale (WURS) is a 25-item self-report questionnaire for the retrospective assessment of childhood attention-deficit hyperactivity disorder (ADHD) symptoms; high scores indicate greater symptoms. The current study used 35 male Veterans Affairs outpatients to determine if WURS scores were associated with objective measures of current attentional functioning, including the Trail Making Test, Gordon Diagnostic System, Wechsler Adult Intelligence Scale-Revised digit span and digit symbol subtests, and Wechsler Memory Scale-Revised mental control subtest. Participants included both adults diagnosed with ADHD (n = 14) and non-ADHD adults (n = 21). After Bonferroni correction, Pearson product moment correlation coefficients revealed that greater symptoms on the WURS were associated with poorer digit symbol performance (r = -0.69, P < .05). To determine which indices best predicted WURS scores, scores on attention tests and demographic variables were entered into a stepwise multiple regression analysis. Digit symbol performance was the only significant predictor of WURS scores (R(2) = 0.59, P < .01). Thus, poor performance on a sensitive, but nonspecific, measure of attention with executive function, response speed, and visuomotor coordination components was related to greater self-report of childhood ADHD symptoms.

Aufmerksamkeitsdefizit-/Hyperaktivitätsstörung (ADHS): Wie valide sind die Subtypen?

Zusammenfassung. Bereits mit Erscheinen des DSM-IV wurde die Validität der dort benannten Subtypen der ADHS hinterfragt. Hinzu kommt eine abweichende Subgruppenbildung in der ICD-10. Seitdem sind die Subtypen in verschiedenen Zusammenhängen untersucht worden. Dabei festgestellte Unterschiede und Gemeinsamkeiten der Subtypen werden aus sechs Perspektiven (verhaltensbezogen, genetisch, geschlechtsspezifisch, entwicklungsbezogen, neurobiologisch, neuropsychologisch) betrachtet, um Informationen über mögliche notwendige Veränderungen im DSM-V zu erlangen. Die Befunde legen zunächst nahe, sich bei zukünftigen Klassifikationskriterien nicht auf die Verhaltensebene zu beschränken, sondern insbesondere neuropsychologische aber auch neurobiologische Aspekte einzubeziehen. So wird unter Berücksichtigung dieser Ebenen für den bisherigen vorwiegend unaufmerksamen Subtyp eine weitere Differenzierung angedeutet: in eine Gruppe mit verlangsamtem kognitiven Tempo, die eventuell sogar eine eigenständige Störung darstellt, sowie einen vorwiegend unaufmerksamen Subtyp der ADHS, der aber schwache Symptome der Hyperaktivität und Impulsivität aufweist. Des Weiteren deutet sich zwar auf einigen Ebenen ein eigenständiger Subtyp ADHS mit komorbiden Störungen des Sozialverhaltens beziehungsweise einer Hyperkinetischen Störung des Sozialverhaltens an. Jedoch sind Befunde anderer Ebenen noch nicht eindeutig und somit ist weitere Forschung notwendig. Zudem scheinen gesonderte Kriterien für die Geschlechter nicht erforderlich, vielmehr sollte stärker beachtet werden, dass auch Mädchen diese Störung aufweisen können. Abschließend werden Implikationen für zukünftige Klassifikationen und ihre Bedeutung für unterschiedliche Behandlungsverfahren diskutiert.

Executive functions and methylphenidate response in subtypes of attention-deficit/hyperactivity disorder

BACKGROUND

Oculomotor tasks are a well-established means of studying executive functions and frontal-striatal functioning in both nonhuman primates and humans. Attention-deficit/hyperactivity disorder (ADHD) is thought to implicate frontal-striatal circuitry. We used oculomotor tests to investigate executive functions and methylphenidate response in two subtypes of ADHD.

METHODS

Subjects were boys, aged 11.5-14 years, with ADHD-combined (n = 10), ADHD-inattentive (n = 12), and control subjects (n = 10). Executive functions assessed were motor planning (tapped with predictive saccades), response inhibition (antisaccades), and task switching (saccades-antisaccades mixed).

RESULTS

The ADHD-combined boys were impaired relative to control subjects in motor planning (p < .003) and response inhibition (p < .007) but not in task switching (p > .92). They were also significantly impaired relative to ADHD-inattentive boys, making fewer predictive saccades (p < .03) and having more subjects with antisaccade performance in the impaired range (p < .04). Methylphenidate significantly improved motor planning and response inhibition in both subtypes.

CONCLUSIONS

ADHD-combined but not ADHD-inattentive boys showed impairments on motor planning and response inhibition. These deficits might be mediated by brain structures implicated specifically in the hyperactive/impulsive symptoms. Methylphenidate improved oculomotor performance in both subtypes; thus, it was effective even when initial performance was not impaired.

Accuracy of self-evaluation in adults with ADHD: evidence from a driving study

Research on children with ADHD indicates an association with inaccuracy of self-appraisal. This study examines the accuracy of self-evaluations in clinic-referred adults diagnosed with ADHD. Self-assessments and performance measures of driving in naturalistic settings and on a virtual-reality driving simulator are used to assess accuracy of self-evaluations. The group diagnosed with ADHD (n= 44) has a higher rate of collisions, speeding tickets, and total driving citations in their driving history; report less use of safe driving behaviors in naturalistic settings; and use fewer safe driving behaviors in the simulator than the community comparison group (n= 44). Despite poorer performance, adults with ADHD provide similar driving self-assessments, thereby overestimating in naturalistic settings to a greater degree than the comparison group. These findings extend research in children with ADHD to an adult sample in an important domain of functioning and may relate to findings of executive deficits associated with ADHD.

Time estimation and performance on reproduction tasks in subtypes of children with attention deficit hyperactivity disorder

This study compared Hispanic children (ages 7 to 11) with combined type (CT, n=33) and inattentive type (IT, n=21) attention deficit hyperactivity disorder (ADHD) and a control group (n=25) on time-estimation and time-reproduction tasks. The ADHD groups showed larger errors in time reproduction but not in time estimation than the control group, and the groups did not differ from each other on their performance on this task. Individual differences could not be accounted for by oppositional-defiance ratings and low math or reading scores. Although various measures of executive functioning did not make significant unique contributions to time estimation performance, those of interference control and nonverbal working memory did so to the time-reproduction task. Findings suggest that ADHD is associated with a specific impairment in the capacity to reproduce rather than estimate time durations and that this may be related to the children's deficits in inhibition and working memory.

Executive Functioning in Hyperactive Children as Young Adults: Attention, Inhibition, Response Perseveration, and the Impact of Comorbidity

Tests of several executive functions (EFs) as well as direct observations of symptoms of attention deficit hyperactivity disorder (ADHD) during testing were collected at the young adult follow-up (M = 20 years) on a large sample of hyperactive (H; N = 147) and community control (CC; N = 71) children. The EF tasks included tests of attention, inhibition, and response perseveration. The H group was subdivided into those with and without ADHD (+ or w/o) at follow-up. The H+ADHD group made significantly more inhibition errors than the CC group on a Continuous Performance Test (CPT) and showed more ADHD symptoms while performing the CPT. The H+ADHD group also displayed more ADHD symptoms during a letter cancellation task than did both the hyperactive w/o ADHD and CC groups. Both H groups showed slower reaction times during a Card Playing Task. That subset of hyperactive probands with Conduct Disorder (CD) displayed significantly more perseverative responding on that task than did those without CD, but otherwise it did not differ on any other measures. Current level of anxiety contributed adversely to both CPT commission errors and ADHD behavior during the CPT. Comorbid depression did not contribute to any group differences on these tests. Although developmental improvements were found in both the H and the CC groups in their CPT inattention and inhibition scores since adolescence, the H groups remained distinguishable from the CC groups over this period. We conclude that formerly hyperactive children manifest greater EF deficits at follow-up in the areas of inattention, disinhibition, and slowed reaction time and greater ADHD behavior during testing, but these problems are mostly confined to those with current ADHD. Response perseveration, however, was limited to those hyperactive children with CD by follow-up, consistent with Quay's theory of these two disorders.

Cognitive-neuropsychological function in chronic physical aggression and hyperactivity

Histories of violence and of hyperactivity are both characterized by poor cognitive-neuropsychological function. However, researchers do not know whether these histories combine in additive or interactive ways. The authors tested 303 male young adults from a community sample whose trajectories of teacher-rated physical aggression and motoric hyperactivity from kindergarten to age 15 were well defined. No significant interaction was found. In a 1st model, both histories of problem behavior were independently associated with cognitive-neuropsychological function in most domains. In a second model controlling for IQ, General Memory, and test motivation, none of the three Working Memory tests (relevant to executive function) remained associated with physical aggression or hyperactivity. These results support an additive model but no specificity to executive function [corrected].

Effect of methylphenidate on executive functioning in adults with attention-deficit/hyperactivity disorder: normalization of behavior but not related brain activity

BACKGROUND

We examined the effect of prolonged methylphenidate (MPH) treatment on the functional neuroanatomy of executive functioning in adult men with attention-deficit/hyperactivity disorder (ADHD).

METHODS

Positron emission tomography with [(15)O] water measured alterations of regional cerebral blood flow (rCBF) during the Paced Auditory Serial Addition Task and a control task in 10 ADHD and 11 normal control men. Attention-deficit/hyperactivity disorder men were imaged unmedicated and after a clinically optimal dose of MPH for 3 weeks.

RESULTS

Methylphenidate improved ADHD task performance, reduced rCBF in the prefrontal cortex (PFC), and increased rCBF in the right thalamus and precentral gyrus. Comparisons between the ADHD and normal control groups showed that normal control participants exhibited greater anterior cingulate cortex and temporal gyrus rCBF than ADHD participants under both conditions. Executive functioning was associated with greater subcortical (basal ganglia and cerebellar vermis) activation in the ADHD than normal control group under both conditions.

CONCLUSIONS

Methylphenidate does not normalize task-related activity in ADHD. Task-related rCBF decreases in the PFC may be due to improved filtering out of task-irrelevant stimuli by way of MPH-mediated dopamine release in the PFC.

Neuropsychology of adults with attention-deficit/hyperactivity disorder: a meta-analytic review

A comprehensive, empirically based review of the published studies addressing neuropsychological performance in adults diagnosed with attention-deficit/hyperactivity disorder (ADHD) was conducted to identify patterns of performance deficits. Findings from 33 published studies were submitted to a meta-analytic procedure producing sample-size-weighted mean effect sizes across test measures. Results suggest that neuropsychological deficits are expressed in adults with ADHD across multiple domains of functioning, with notable impairments in attention, behavioral inhibition, and memory, whereas normal performance is noted in simple reaction time. Theoretical and developmental considerations are discussed, including the role of behavioral inhibition and working memory impairment. Future directions for research based on these findings are highlighted, including further exploration of specific impairments and an emphasis on particular tests and testing conditions.

Meta-analysis of intellectual and neuropsychological test performance in attention-deficit/hyperactivity disorder

Cognitive measures are used frequently in the assessment and diagnosis of attention-deficit/hyperactivity disorder (ADHD). In this meta-analytic review, the authors sought to examine the magnitude of differences between ADHD and healthy participants on several commonly used intellectual and neuropsychological measures. Effect sizes for overall intellectual ability (Full Scale IQ; FSIQ) were significantly different between ADHD and healthy participants (weighted d =.61). Effect sizes for FSIQ were significantly smaller than those for spelling and arithmetic achievement tests and marginally significantly smaller than those for continuous performance tests but were comparable to effect sizes for all other measures. These findings indicate that overall cognitive ability is significantly lower among persons with ADHD and that FSIQ may show as large a difference between ADHD and control participants as most other measures.

The utility of self-report measures and the continuous performance test in the diagnosis of ADHD in adults

BACKGROUND

Attention-deficit/hyperactivity disorder (ADHD) occurs in as many as 4 percent of adults yet it is often not recognized in clinical settings because the presenting symptoms may resemble those seen in other disorders or because symptoms may be masked by commonly comorbid conditions such as anxiety and depression.

OBJECTIVE

The purpose of this study was to examine the diagnostic utility of instruments commonly used in the assessment of adults presenting with symptoms of ADHD.

METHODS

We reviewed several widely used self-report and laboratory measures and empirically examined the utility of the Brown Attention-Deficit Disorder Scale for Adults (Brown ADD Scale) and the Conners Continuous Performance Test (CPT) in differentially identifying adults with ADHD and those with other Axis I disorders.

RESULTS

Ninety-three adults who self-referred to the ADHD program for adults at a university medical center participated in the study. Of these, 44 had ADHD combined subtype (ADHD-CB), and 26 had ADHD, predominantly inattentive subtype (ADHD-IA). Thirty-three non-ADHD adults diagnosed with Axis I mood or anxiety disorders comprised an "Other Psychiatric" group. Rates of comorbid disorders, including substance abuse, in the ADHD groups were typical of those reported in the adult ADHD literature. Data on the Brown ADD Scale and on the CPT were available for subsets of 61 and 46 participants, respectively. Analyses showed that the ADHD-CB, ADHD-IA, and Other Psychiatric groups all received mean scores in the clinical range on the Brown ADD Scale, with a trend toward even higher elevations in the two ADHD groups. Among 12 CPT variables assessed for the three groups, the mean scores on only two variables for the ADHD-IA group were clinically elevated. Neither the Brown ADD Scale nor CPT scores evinced sufficient sensitivity and specificity to qualify them to assist in differential diagnosis of ADHD vis-a-vis other, predominantly internalizing, psychiatric disorders.

CONCLUSION

The results indicate a need for closer examination of executive and adaptive functioning in adults with ADHD compared with those with internalizing disorders in order to identify features that could assist in differential diagnosis.

Neuropsychological function in adults with attention-deficit/hyperactivity disorder

This article reviews the current state of the literature pertaining to the neuropsychological dysfunctions that are found in children and adults with attention-deficit/hyperactivity disorder (ADHD). Be-cause considerable controversy has existed about the nature and validity of adult ADHD, this article will aid clinicians in develop-ing a better understanding of the empirical literature on neuropsychological function in ADHD throughout the lifespan.

Driving impairments in teens and adults with attention-deficit/hyperactivity disorder

Available research provides compelling evidence that ADHD is associated with significantly increased risks for various adverse outcomes while driving, including increased traffic citations (particularly speeding), motor vehicle crashes for which the driver is at fault, repeated crash occurrences,and more severe crashes as determined from dollar damage and likelihood of bodily injuries from the crash. Not surprisingly, teens and adults with ADHD are more likely to have their licenses suspended and even fully revoked. Research further suggests that these driving risks cannot be accounted for by the comorbid disorders likely to be associated with ADHD, such as ODD, conduct disorder (CD), depression, or anxiety, or by lower than normal levels of intelligence. Recent attempts to study the processes or mechanisms involved in driving in adults with ADHD offer some explanation of how the disorder conveys such increased risks. Driving can be conceptualized usefully as involving at least three or more dimensions or levels, including basic cognitive abilities necessary for driving (operational), actual skills for maneuvering the vehicle in traffic (tactical), and the more executive, goal-directed aspects of driving(strategic). The findings of studies indicate that ADHD interferes with the basic operational components of driving by means of the impairments it produces in attention, resistance to distraction, response inhibition, slower and more variable reaction time, and the capacity to follow rules that may compete with ongoing sensory information. Accumulating evidence also points to a problem in the tactical level of driving, such that those with ADHDrate themselves and are rated by others as employing less safe driving habits during their normal operation of a vehicle than are adults in community control groups. Although this has been more elusive to demonstrate through the use of simple laboratory-based driving simulators. more modern virtual reality driving platforms offer greater promise in providing more realistic appraisals of driving performance and thus more direct evidence of the problems that occur at the tactical level from the disorder. Research has not examined the impact of ADHD at the higher strategic level or goal-directed aspects of driving. But given the mounting evidence that ADHD adversely affects executive functioning in adults, the author and colleagues anticipate that this level also will be found to be impaired in adults with ADHD. Indeed,it recently has been shown that adults with ADHD overestimate their driving abilities relative to normal adults, a problem that likely can be ascribed to more limited self-awareness and related meta-cognitive abilities for self-evaluation arising from the disorder. Although further research on the driving problems posed by ADHD is in order, sufficient evidence exists to warrant focus on possible treatments that may serve to improve these driving problems and reduce the risk for these adverse outcomes. High on the list of such treatments deserving further research and clinical attention is the use of stimulant medication. The more recent noradrenergic reuptake inhibitor. atomoxetine, also may have some promise in this regard. Studies are underway in the author's driving laboratory to see if this is the case. Meanwhile, adults with ADHD and parents of teens with ADHD should be advised about these heightened risks and encouraged to take steps that may reduce them, including the consideration of more graduated licensing for adolescents with ADHD and the possible use of stimulant medication in teens and adults with ADHD while they are operating a motor vehicle.

Pathological gambling: a comprehensive review of biobehavioral findings

In this review, findings of biobehavioral research into pathological gambling (PG) are discussed, focusing on neuropsychological, psychophysiological, neuroimaging, neurochemical and genetic studies. Neuropsychological studies indicate deficiencies in certain executive functions. Psychophysiological studies indicate that arousal in PG is of importance when reward is present. Neuroimaging studies point to abnormalities in brain functioning. Recent research into the neurochemistry of PG indicates that abnormalities exist in different neurotransmitter systems. Finally, genetic studies indicate the existence of abnormal dopamine receptor genes in PG. Methodological and theoretical factors that may explain discrepancies between studies include differences in screening and assessment, heterogeneity of gambling problems and different underlying cognitive or motivational mechanisms. Results from the PG studies fit in with recent theoretical models of addiction and PG, which stress the involvement of brain reward pathways, neurotransmitter abnormalities, the frontal cortex and the psychophysiological stress system. A framework for future studies is suggested, indicating the need for studies that integrate knowledge from different research areas, and that employ stricter diagnostic screening methods and inclusion of clinical control groups.

Executive dysfunction in attention-deficit/hyperactivity disorder: cognitive and neuroimaging findings

Attention-deficit/hyperactivity disorder has been associated with a prominent disturbance of executive functions. There is no pathognomic neuropsychological profile for the disorder, however. Nonetheless, results of neuropsychological testing, in concert with other clinical information,provide a more comprehensive and detailed picture of the individual patient's cognitive and emotional strengths and weaknesses than a psychiatric diagnostic interview alone. This approach to the evaluation of ADHD therefore can provide a strong objective basis from which to make patient-specific recommendations for compensatory strategies and treatment. It should be noted, however, that although executive dysfunction in the form of impaired response inhibition remains the most prominent cognitive theory of ADHD, other theories have been put forth that also deserve further investigation. These include a disturbance in delay aversion (referring to intolerance for waiting) and impaired temporal processing, among others [79]. The neural substrates of executive dysfunction in ADHD have begun to be revealed by a growing body of structural and functional neuroimaging research. Although still in its infancy, neuroimaging of ADHD is pointing toward disruption of FSTC circuitry and the cerebellum as being central to the cognitive and motor abnormalities seen in the disorder. Further research using cognitive tasks assessing executive functions in combination with functional imaging techniques will provide further insight into the etiology of the disorder. It is expected that advances in structural and functional neuroimaging will yield valuable information that will facilitate the differential diagnosis of ADHD. Evidence cited suggests that psychostimulant medication can improve executive functions and their underlying FSTC circuitry. Furthermore, a recent study of adults with ADHD found significant improvements in organization skills and other symptoms of ADHD following cognitive remediation targeting several executive and emotional aspects of the disorder [80]. Additional studies investigating the effects of treatment on executive dysfunction and brain integrity in ADHD will be necessary to determine the degree to which the structural and functional brain abnormalities observed are mutable. Finally, because the myriad cognitive, behavioral and emotional symptoms in ADHD likely reflect the interplay of multiple cognitive and psychosocial factors, development of treatments for ADHD likely will require a multi-modal approach.

Contribution of Organizational Strategy to Verbal Learning and Memory in Adults With Attention-Deficit/Hyperactivity Disorder

Statistical mediation modeling was used to test the hypothesis that poor use of a semantic organizational strategy contributes to verbal learning and memory deficits in adults with attention-deficit/hyperactivity disorder (ADHD). Comparison of 28 adults with ADHD and 34 healthy controls revealed lower performance by the ADHD group on tests of verbal learning and memory, sustained attention, and use of semantic organization during encoding. Mediation modeling indicated that state anxiety, but not semantic organization, significantly contributed to the prediction of both learning and delayed recall in the ADHD group. The pattern of findings suggests that decreased verbal learning and memory in adult ADHD is due in part to situational anxiety and not to poor use of organizational strategies during encoding.

Lesions of the medial prefrontal cortex or nucleus accumbens core do not impair inhibitory control in rats performing a stop-signal reaction time task

The 'stop-signal' task measures the ability to inhibit a response that has already been initiated, i.e. the ability to stop. Human subjects who have been classified as 'impulsive', for example, those with attention-deficit/hyperactivity disorder (ADHD), are slower to react to the stop signal, and are often less sensitive to changes in the timing of signals to stop. Imaging studies have implicated fronto-striatal circuitry in the mediation of this form of response control. We report inhibition functions on the stop-signal reaction time (SSRT) task for normal rats, and following damage to the medial prefrontal cortex or to the nucleus accumbens core. Neither group of excitotoxic lesions produced significant deficits on task performance. Subsequent treatment with D-amphetamine (0.3 and 1.0mg/kg) resulted in quicker go-trial reaction times (mRT) overall, but had no significant effect on SSRT. Neither medial prefrontal cortex nor nucleus accumbens lesions had any differential effects on performance following D-amphetamine. These results are discussed with respect to the fronto-striatal circuitry involved in the mediation of behavioural inhibition.

Issues in the diagnosis of attention-deficit/hyperactivity disorder in children

This paper provides a brief overview of the nature of attention-deficit/hyperactivity disorder (ADHD) in children and the current criteria used in its clinical diagnosis. While the disorder continues to be viewed as one of inattention and/or hyperactive-impulsive behavior, theories of ADHD are beginning to focus more on poor inhibition and deficient executive functioning (self-regulation) as being central to the disorder. Problems have been identified by research pertaining to the clinical diagnostic criteria outlined in the DSM-IV that, at present, remain unresolved. Clinicians should be aware of these problems and the adjustments that need to be made to them when dealing with special populations that were not represented in the field trials used to develop these criteria.

Young adults with attention deficit hyperactivity disorder: subtype differences in comorbidity, educational, and clinical history

The present study sought to examine subtype differences in comorbidity and in antisocial, educational, and treatment histories among young adults (ages 17-27) with attention deficit hyperactivity disorder (ADHD). Comparisons were made between ADHD Combined Type (ADHD-C; N = 60) and Predominantly Inattentive Type (ADHD-I; N = 36) relative to each other and to a community control group of 64 adults. Both ADHD groups had significantly less education, were less likely to have graduated from college, and were more likely to have received special educational placement in high school. Both groups also presented with a greater likelihood of dysthymia, alcohol dependence/abuse, cannabis dependence/abuse, and learning disorders, as well as greater psychological distress on all scales of the SCL-90-R than the control group. Both ADHD groups were more likely to have received psychiatric medication and other mental health services than control adults. In comparison with ADHD-I, adults with ADHD-C differed in only a few respects. The C-type adults were more likely to have oppositional defiant disorder, to experience interpersonal hostility and paranoia, to have attempted suicide, and to have been arrested than the ADHD-I adults. These results are generally consistent with previous studies of ADHD in children, extend these findings to adults with ADHD, and suggest that the greater impulsivity associated with the ADHD-C subtype may predispose toward greater antisocial behavior and its consequences than does ADHD-I type in adults.

Executive functioning, temporal discounting, and sense of time in adolescents with attention deficit hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD)

Clinic-referred teens (ages 12-19) with ADHD and ODD (N = 101) were compared to community control (CC) teens, equated for age and sex, (N = 39) on a variety of psychological tasks assessing executive functioning (EF), temporal reward discounting, and time estimation and reproduction. A factor analysis reduced the EF measures to three dimensions, representing CPF Inattention, Working Memory, and CPT Inhibition. Results indicated that the ADHD group had significantly more CPT Inattention than the CC group. No differences were found for Working Memory or CPT Inhibition. The ADHD group displayed significantly greater temporal discounting of delayed hypothetical monetary rewards relative to immediate ones and manifested more impaired time reproduction, but not time estimation, than did the CC group. Main effects for level of IQ were found only on the Working Memory factor and largely did not interact with the group factor otherwise. The group differences in CPT Inattention, temporal discounting, and time reproduction were not a function of level of comorbid oppositional defiant disorder, delinquency, or anxiety-depression. Results are reasonably consistent with past research on EF and sense of time in children with ADHD and extend these findings to the adolescent age group. Problems with working memory and CPT inhibition found in prior studies of children with ADHD, however, were not evident here, perhaps owing to age-related improvements or insufficient task difficulty.

Time perception and reproduction in young adults with attention deficit hyperactivity disorder

Adults with attention deficit hyperactivity disorder (ADHD; n = 104) were compared with a control group (n = 64) on time estimation and reproduction tasks. Results were unaffected by ADHD subtype or gender. The ADHD group provided larger time estimations than the control group, particularly at long intervals. This became nonsignificant after controlling for IQ. The ADHD group made shorter reproductions than did the control group (15- and 60-s intervals) and greater reproduction errors (12-, 45-, 60-s durations). These differences remained after controlling for IQ and comorbid oppositional defiant disorder, depression, and anxiety. Only the level of anxiety contributed to errors (at 12-s duration) beyond the level of ADHD. Results extended findings on time perception in ADHD children to adults and ruled out comorbidity as the basis of the errors.