Attention-deficit hyperactivity disorder comorbidity and antidepressant resistance among patients with major depression: A nationwide longitudinal study.

The comorbidity between attention deficit hyperactivity disorder (ADHD) and major depression is common. However, the influence of ADHD comorbidity in the response or resistance to antidepressants remains unknown among patients with major depression. 1891 patients with major depression and ADHD and 1891 age-/sex-matched patients with major depression only were enrolled and followed for 1 year in our study. Use of antidepressants and ADHD medications during 1-year follow-up period were assessed. Antidepressant resistance was defined as treatment failure in two or more than two different antidepressants for adequate treatment dose and duration. Patients with major depression and ADHD had an increased risk of treatment resistance to antidepressants (odds ratio [OR]: 2.32, 95% confidence interval [CI]: 1.63-3.32) compared with patients with major depression only after adjusting for demographic characteristics and other psychiatric comorbidities. Regular treatment for ADHD would reduce this risk (OR: 1.76, 95% CI: 0.72-4.27). Anxiety (OR: 3.15, 95% CI: 2.24-4.44) and substance use (OR: 2.45, 95% CI: 1.16-5.17) disorders were also associated with an elevated likelihood of resistance to antidepressants during the follow-up. Patients who had dual diagnoses of major depression and ADHD were more likely to have treatment resistance to antidepressants compared with patients with major depression only. Prompt and regular treatment for ADHD would reduce this risk.