Which comorbidity is most commonly associated with major depressive disorder and worsens prognosis?

• A. Generalized anxiety disorder
• B. Obsessive-compulsive disorder
• C. Substance use disorder (alcohol or other substances)
• D. Schizophrenia

Answer: (C)

Co-occurring substance use disorders commonly accompany major depressive disorder and worsen prognosis. People with depression often use alcohol or other drugs to cope with distress, but continued use amplifies mood symptoms, disrupts sleep, and impairs functioning. This creates a cycle of withdrawal, cravings, and intoxication that makes depressive episodes harder to treat, increases relapse risk, and complicates recovery by reducing medication effectiveness and complicating psychotherapy. Substance use also raises medical and social problems, which feed back into greater depressive symptom severity. While other conditions like generalized anxiety, OCD, or schizophrenia can occur with depression, they do not typically have the same broad, consistent impact on the course and outcome as a comorbid substance use disorder.