CONTEXT: Although children with attention-deficit/hyperactivity disorder (ADHD) are at elevated risk for comorbid psychopathology, the clinical correlates of ADHD in girls are far less understood relative to boys, despite ADHD being one of the most common childhood disorders in girls.OBJECTIVE: To meta-analytically summarize rates of comorbid internalizing (anxiety, depression) and externalizing (oppositional defiant disorder [ODD], conduct disorder [CD]) psychopathology among girls with and without ADHD.DATA SOURCES: Literature searches (PubMed, Google Scholar) identified published studies examining comorbid psychopathology in girls with and without ADHD. STUDY SELECTION:Eighteen studies (1997 participants) met inclusion criteria and had sufficient data for the meta-analysis. DATA EXTRACTION:Odds ratios for each comorbid disorder were calculated from available data. Demographic (eg, age, race/ethnicity) and study characteristics (eg, referral source, diagnostic method) were also coded. RESULTS:Compared with girls without ADHD, girls with ADHD were significantly more likely to meet Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria for each comorbid disorder assessed. Relative odds were higher for externalizing (ODD: 5.6×; CD: 9.4×) relative to internalizing disorders (anxiety: 3.2×; depression: 4.2×). Meta-regression revealed larger effect sizes of ADHD on anxiety for studies using multiple diagnostic methods, featuring younger children, and including clinic-referred (versus communityreferred) girls; the effect of ADHD on ODD varied based on diagnostic informant. LIMITATIONS:Findings were derived from cross-sectional studies, precluding causal inferences.CONCLUSIONS: Girls with ADHD frequently exhibit comorbid externalizing and internalizing disorders. We discuss future research priorities and consider intervention implications for ADHD and comorbid psychopathology in girls. Ms Tung collected and coded studies for inclusion, supervised the acquisition of data, carried out the analyses, and drafted the initial manuscript; Dr Li conceptualized and designed the study, supervised the acquisition of data, assisted with interpretation of analyses, and critically reviewed and revised the manuscript; Ms Meza and Ms Jezior collected and coded the studies for inclusion, assisted with drafting the initial manuscript, and reviewed and revised the manuscript; Ms Kianmahd, Mr Hentschel, and Mr O'Neil collected and coded the studies for inclusion and reviewed and revised the manuscript; Dr Lee supervised the acquisition of data, assisted with interpretation of analyses, and critically reviewed and revised the manuscript; and all authors approved the fi nal manuscript as submitted.

Although narcissism and callous-unemotional (CU) traits are separable facets of psychopathy, their independent prediction of conduct problems (CP) among young children is not well known. In addition, above-average IQ was central to the original conceptualization of psychopathy, yet IQ is typically inversely associated with youth CP. We examined narcissism and CU traits as independent and prospective predictors of oppositional defiant disorder (ODD), conduct disorder (CD), and youth self-reported antisocial behavior, as well as their moderation by IQ. At baseline, parents and teachers separately rated narcissism and CU traits in 188 6-to-10-year-old children (47.9% non-White; 69.1% male; M = 7.34 years, SD = 1.09) with (n = 99) and without (n = 89) attention-deficit/hyperactivity disorder (ADHD). Approximately 2 years later, parents and teachers separately rated youth ODD and CD symptoms, and youth self-reported antisocial behavior. With control of baseline ADHD and ODD/CD symptoms, narcissism and CU traits independently and positively predicted ODD and CD symptoms at follow-up. IQ did not moderate any CP predictions from baseline narcissism or CU traits. These preliminary findings suggest that individual differences in narcissism and CU traits, even relatively early in development, are uniquely associated with emergent CP. Findings are considered within a developmental framework and the multiple pathways underlying the heterogeneity of CP are discussed.

Although the promoter polymorphism of the serotonin transporter (5-HTTLPR) gene is associated with externalizing behavior, its mediating pathways are unknown. Given their sensitivity to serotonin neurotransmission and unique association with attention-deficit/hyperactivity disorder (ADHD) and oppositional defiant disorder (ODD), we tested callous-unemotional (CU) traits and narcissism as separate mediators of the association of 5-HTTLPR with ADHD and ODD. We evaluated 209 5–9 year-old children with and without ADHD at baseline; approximately two years later (i.e., Wave 2), parents and teachers separately rated ADHD and ODD symptoms and youth self-reported antisocial behavior. Controlling for race-ethnicity and baseline ADHD/ODD, narcissism uniquely mediated predictions of multi-informant rated Wave 2 ADHD and ODD from variation in 5-HTTLPR; CU traits mediated predictions of Wave 2 ADHD from variations in 5-HTTLPR, but did not mediate the associations of 5-HTTLPR with ODD or youth self-reported antisocial behavior. Specifically, the number of 5-HTTLPR long alleles positively predicted CU traits and narcissism; narcissism was positively associated with Wave 2 ADHD and ODD symptoms, whereas CU traits were positively associated with Wave 2 ADHD. Child sex also moderated indirect effects of CU traits and narcissism, such that narcissism mediated predictions of ADHD/ODD in girls but not boys. Psychopathic traits may represent a relevant pathway underlying predictions of prospective change in ADHD and ODD from 5-HTTLPR, particularly in girls. We consider the role of psychopathic traits as a potential intermediate phenotype in genetically-sensitive studies of child psychopathology.