DSM-IV criteria for ADHD specify two dimensions of inattention and hyperactivity-impulsivity symptoms that are used to define three nominal subtypes: predominantly hyperactive-impulsive type (ADHD-H), predominantly inattentive type (ADHD-I), and combined type (ADHD-C). To aid decision-making for DSM-5 and other future diagnostic systems, a comprehensive literature review and meta-analysis of 546 studies was completed to evaluate the validity of the DSM-IV model of ADHD. Results indicated that DSM-IV criteria identify individuals with significant and persistent impairment in social, academic, occupational, and adaptive functioning when intelligence, demographic factors, and concurrent psychopathology are controlled. Available data overwhelmingly support the concurrent, predictive, and discriminant validity of the distinction between inattention and hyperactivity-impulsivity symptoms, and indicate that nearly all differences among the nominal subtypes are consistent with the relative levels of inattention and hyperactivity-impulsivity symptoms that define the subtypes. In contrast, the validity of the DSM-IV subtype model is compromised by weak evidence for the validity of ADHD-H after first grade, minimal support for the distinction between ADHD-I and ADHD-C in studies of etiological influences, academic and cognitive functioning, and treatment response, and the marked longitudinal instability of all three subtypes. Overall, it is concluded that the DSM-IV ADHD subtypes provide a convenient clinical shorthand to describe the functional and behavioral correlates of current levels of inattention and hyperactivity-impulsivity symptoms, but do not identify discrete subgroups with sufficient long-term stability to justify the classification of distinct forms of the disorder. Empirical support is stronger for an alternative model that would replace the subtypes with dimensional modifiers that reflect the number of inattention and hyperactivity-impulsivity symptoms at the time of assessment.

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Objective To examine the efficacy of a 12-week manualized Meta-Cognitive Therapy (MCT) group designed to enhance time-management, organization, and planning in adults with AD/HD. Method Eighty-eight clinically referred adults who met DSM-IV criteria for ADHD based on clinical and structured diagnostic interviews and standardized questionnaires were stratified vis-à-vis ADHD medication use and otherwise randomly assigned to receive MCT or supportive psychotherapy in a group modality. MCT employs cognitive-behavioral principles and methods to impart skills and strategies in time-management, organization, and planning, and target depressogenic and anxiogenic cognitions that undermine effective self-management. The Support group controlled for non-specific aspects of treatment by providing support while avoiding discussion of cognitive-behavioral strategies. MCT and Support groups were comparable in gender (29% and 39% male, respectively) and age (41±11.59 yr and 42 ± 12.09 years, respectively). Therapeutic response was assessed by an independent (blind) evaluator via structured interview pre- and post-treatment, as well as by self-report and collateral informant behavioral ratings. Results General linear models, comparing change from baseline between treatments, revealed statistically significant effects for independent evaluator, self-report, and collateral ratings of DSM-IV inattentive symptoms. Employing dichotomous indices of therapeutic response, a significantly greater proportion of MCT vs. Support group members demonstrated improvement. Logistic regression examining group differences in operationally defined response (controlling for baseline ADHD severity) revealed a robust effect of Treatment Group (odds ratio=5.41; 95%CI=1.77,16.55). Conclusion MCT (vs. Support) yielded significantly greater improvements in dimensional and categorical estimates of ADHD severity, supporting its efficacy as a viable psychosocial intervention.

Context: Attention-deficit/hyperactivity disorder (ADHD) is the most prevalent psychiatric disorder of childhood. There is considerable evidence that brain dopamine is involved in ADHD, but it is unclear whether dopamine activity is enhanced or depressed.Objective: To test the hypotheses that striatal dopamine activity is depressed in ADHD and that this contributes to symptoms of inattention.Design: Clinical (ADHD adult) and comparison (healthy control) subjects were scanned with positron emission tomography and raclopride labeled with carbon 11 (D 2 /D 3 receptor radioligand sensitive to competition with endogenous dopamine) after placebo and after intravenous methylphenidate hydrochloride (stimulant that increases extracellular dopamine by blocking dopamine transporters). The difference in [11 C]raclopride's specific binding between placebo and methylphenidate was used as marker of dopamine release. Symptoms were quantified using the Conners Adult ADHD Rating Scales.Setting: Outpatient setting.Participants: Nineteen adults with ADHD who had never received medication and 24 healthy controls.Results: With the placebo, D 2 /D 3 receptor availability in left caudate was lower (PϽ.05) in subjects with ADHD than in controls. Methylphenidate induced smaller decrements in [11 C]raclopride binding in left and right caudate (blunted DA increases) (P Ͻ .05) and higher scores on self-reports of "drug liking" in ADHD than in control subjects. The blunted response to methylphenidate in caudate was associated with symptoms of inattention (P Ͻ .05) and with higher self-reports of drug liking (PϽ.01). Exploratory analysis using statistical parametric mapping revealed that methylphenidate also decreased [11 C]raclopride binding in hippocampus and amygdala and that these decrements were smaller in subjects with ADHD (PϽ .001).Conclusions: This study reveals depressed dopamine activity in caudate and preliminary evidence in limbic regions in adults with ADHD that was associated with inattention and with enhanced reinforcing responses to intravenous methylphenidate. This suggests that dopamine dysfunction is involved with symptoms of inattention but may also contribute to substance abuse comorbidity in ADHD. Psychiatry. 2007;64(8):932-940 Arch Gen

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Impulsivity is a primary symptom of the combined type of Attention Deficit/Hyperactivity Disorder (AD/HD). The Stop Signal Paradigm is premised upon a primary deficit in inhibitory control in AD/HD, whereas the Delay Aversion Hypothesis, by contrast, conceptualizes impulsivity in AD/HD, not as an inability to inhibit a response, but rather as a choice to avoid delay. This study compared the ecological validity of the Stop Signal Task (SST) and Choice-Delay Task (C-DT) measure of delay aversion, with respect to their relative utility in discriminating AD/HD children from normal control participants, and their correlations with classroom observations and with ratings of impulsivity and other core AD/HD symptoms on the Conners and SNAP-IV checklists. The tasks exhibited modest discriminant validity when used individually and excellent discriminant validity when used in combination. The C-DT correlated with teacher ratings of impulsivity, hyperactivity, and conduct problems, and with observations of gross motor activity, physical aggression, and an AD/HD composite score. The SST correlated with the observations only. These results suggest that delay aversion is associated with a broad range of AD/HD characteristics whereas inhibitory failure seems to tap a more discrete dimension of executive control.