The co-occurrence of attention-deficit/hyperactivity disorder and unipolar depression in children and adolescents: A meta-analytic review

This paper reviews the empirical literature on the association between attention-deficit/hyperactivity disorder (ADHD) and depression (i.e., unipolar depressive disorders and symptoms) among children and adolescents. Findings from cross-sectional and longitudinal studies published on the co-occurrence of ADHD and depression were summarized and subjected to a meta-analysis. Results (k = 29, N = 8755; rbar = 0.22) indicated that ADHD and depression were positively related, but substantial variability existed across the studies. Subgroup analyses indicated medium positive effects for cross-sectional studies, studies that operationalized ADHD based on DSM-III or DSM-IV diagnostic criteria, and studies that did not include teacher report in the assessment of ADHD. Subgroup analyses showed a large positive effect for studies that operationalized ADHD based on DSM-III-R criteria and studies using clinic referred samples. In contrast, subgroup analyses indicated a small negative and/or unreliable association between ADHD and depression for longitudinal studies, studies using DSM-II diagnostic criteria for hyperkinetic reaction of childhood or used a dichotomous motor hyperactivity criterion, studies that used nonreferred samples, and studies including teacher report in the assessment of ADHD. When studies that used DSM-II diagnostic criteria were removed, a reliable medium effect was found for studies that included teacher report. Similarly when the study that used idiosyncratic methods of diagnosing ADHD was excluded, a reliable medium effect was found for studies that used nonreferred samples. Potential explanations for the findings are discussed, including explanations based on sampling and base rates, artifacts of diagnostic criteria, inaccurate diagnostic boundaries, and etiological relationships. Directions for future research and clinical implications are discussed.