Worldwide, depressive disorders are highly prevalent, about 60% of persons with remitted depression experience recurrence, and 24.5% develop chronic depression.
ADHD is a risk factor for depressive disorders, childhood ADHD predicted elevated depressive symptoms compared with non-ADHD controls.
18.4% of children diagnosed with ADHD between ages 4 and 6 reported experiencing persistent depressive episodes by age 18 compared with 1.6% of children in a healthy control group.
ADHD is associated with elevated rates of comorbid depression with roughly 16% to 31% of adults with ADHD also experiencing the major depressive disorder.
However, not all adults with ADHD experience comorbid depression. 18% of adults with ADHD were resilient to developing any comorbid depressive disorder, despite significant ADHD symptoms and related impairments.
Although symptoms overlap between depression and ADHD, the majority of persons with ADHD have shown to maintain their diagnosis when overlapping symptoms with depression were subtracted. For example, hyperactive and/or impulsive behaviors are not part of the diagnostic criteria for depression. For differential diagnosis, it is important that ADHD starts early in childhood and has a chronic course, whereas depression usually starts later and has an episodic course.
A longer period of past ADHD treatment would predict resilience to depression, some works indicate that treatment of ADHD earlier in development may be a protective factor for the development of later comorbidity. Oddo, L. E., Knouse, L. E., Surman, C. B. H., & Safren, S. A. (2016). Investigating Resilience to Depression in Adults With ADHD. Journal of Attention Disorders, 22(5), 497–505. doi:10.1177/1087054716636937
Meinzer, M. C., Pettit, J. W., Waxmonsky, J. G., Gnagy, E., Molina, B. S., & Pelham, W. E. (2015). Does childhood attention-deficit/hyperactivity disorder (ADHD) predict levels of depressive symptoms during emerging adulthood? Journal of abnormal child psychology, 1-11.
Chronis-Tuscano, A., Molina, B. S., Pelham, W. E., Applegate, B., Dahlke, A., Overmyer, M. A., & Lahey, B. B. (2010). Very early predictors of adolescent depression and suicide attempts in children with attention-deficit/hyperactivity disorder. Archives of General Psychiatry, 67, 1044-1051. doi:10.1001/ archgenpsychiatry.2010.127
Knouse, L. E., Zvorsky, I., & Safren, S. A. (2013). Depression in adults with attention-deficit/hyperactivity disorder (ADHD): The mediating role of cognitive-behavioral factors. Cognitive Therapy and Research, 37, 1220-1232. doi:10.1007/s10608- 013-9569-5
Bron, T. I., Bijlenga, D., Verduijn, J., Penninx, B. W. J. H., Beekman, A. T. F., & Kooij, J. J. S. (2016). Prevalence of ADHD symptoms across clinical stages of major depressive disorder. Journal of Affective Disorders, 197, 29–35. doi:10.1016/j.jad.2016.02.053