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.