The objective of the present study was to examine the association between ADHD severity and the lifetime prevalence of comorbid depressive episodes and anxiety disorders in adults with ADHD.

Analyses were based on data of the Conner's Adult ADHD Rating Scale (CAARS) and a parent study examining the epidemiology of adult ADHD in 17 GP practices in Budapest, Hungary. Subjects between 18 and 60 years were included in the screening phase (n = 3529). Out of 279 positively screened subjects 161 participated in a clinical interview and completed the CAARS to confirm the diagnosis. We applied four diagnostic criteria: “DSM-IV”; “No-onset” (DSM-IV criteria without the specific requirement for onset); “Symptoms-only” (DSM-IV symptom criterion only); and “Reduced symptoms-only” (DSM-IV symptom criterion with a reduced threshold for symptom count). The MINI PLUS 5.0 was used to assess psychiatric comorbidity.

ADHD severity, as measured by the CAARS ADHD Index, showed a significant positive association with the prevalence of comorbid depressive episodes in all but the “ADHD_No-onset” group (“DSM-IV”: F[1.23] = 8.39, P = 0.0081; “No-onset”: F(1.27) = 0.97, P = 0.3346; “Symptoms-only”: F[1.55] = 30.79, P < 0.0001; “Reduced symptoms-only”: F(1.62) = 26.69, P < 0.0001).

Results indicate that ADHD symptom severity increases in association with lifetime comorbidity with depression.