Bipolar symptoms in adult attention-deficit/hyperactivity disorder: a cross-sectional study of 510 clinically diagnosed patients and 417 population-based controls.

OBJECTIVE Bipolar spectrum disorders (BSD) have several symptoms and features in common with attention-deficit/hyperactivity disorder (ADHD). Here we explored the prevalence of BSD and the relationship between symptoms of BSD and ADHD in adult ADHD patients. METHOD Norwegian adults diagnosed with DSM-IV ADHD during 1997 through 2007 (n = 510) and a random sample of 417 controls from the general population (aged 18-40 years) were recruited and responded to 85 questions rating symptoms of ADHD, lifetime symptoms of mood disorders, other comorbid conditions, and sociodemographic data. RESULTS According to the Mood Disorder Questionnaire (MDQ), 50.6% of the ADHD patients screened positive for BSD, compared to 8.3% of the controls. In comparison, the prevalence of BSD according to DSM-IV in a subsample of interviewed patients (n = 50) was 32%. In the whole study sample (N = 927), an ADHD diagnosis was the strongest predictor for screening positive on the MDQ (OR = 5.0, P < .001), but the correlation between dimensional symptom levels of ADHD and of BSD was strongest in the control group (Pearson correlation r = 0.7, P < .001 vs r = 0.3, P < .001). Patients screening positive on the MDQ had significantly more drug problems, higher ADHD symptom scores, and lower educational and occupational levels. CONCLUSIONS Our findings illustrate the close relationship between some symptoms of BSD and ADHD in adults. In clinical and research settings, patients screening positive for BSD should be assessed for a possible underlying or coexisting ADHD condition and vice versa.