Major Depressive Disorder (MDD): Prevalence, Core Symptoms, and Impact

Major Depressive Disorder (MDD) is the most prevalent mood disorder, affecting ~21 million U.S. adults annually (8.4%).

Diagnostic Criteria (DSM-5) – ≥2 Weeks

• Depressed mood or anhedonia (loss of interest/pleasure) – required.
• Plus ≥4 of: weight/appetite change, insomnia/hypersomnia, psychomotor agitation/retardation, fatigue, worthlessness/guilt, concentration difficulty, suicidal ideation.
• Clinically significant distress/impairment.
• Not attributable to substance/medical condition; not better explained by schizoaffective, bipolar.

Severity & Course

• Mild / Moderate / Severe (with/without psychotic features).
• Recurrent (>50% have recurrence); chronic (>2 years) in ~20%.
• Comorbidities: anxiety (60%), substance use, medical illness.

Impact

• Leading cause of disability worldwide (WHO).
• Work loss, relationship strain, healthcare utilization, suicide risk (2–15% lifetime).

Treatment

• Antidepressants (SSRIs first-line), psychotherapy (CBT, BA, IPT), combination.
• Remission achievable in ~60–70% with adequate trials.

Early recognition and sustained treatment restore function and save lives.