Overview
Definition
A common and serious medical illness that negatively affects how you feel, the way you think, and how you act, characterized by persistent sadness and loss of interest.
Epidemiology
Extremely common (lifetime prevalence ~20%). Women are affected twice as often as men.
Etiology & Risk Factors
- Multifactorial: Monoamine hypothesis (deficiency in serotonin, norepinephrine, dopamine), genetic predisposition, environmental stressors (trauma, grief, chronic illness).
Clinical Symptoms
- SIGECAPS (must have ≥ 5 for ≥ 2 weeks, and at least one must be depressed mood or anhedonia):
- Sleep changes (insomnia or hypersomnia)
- Interest loss (Anhedonia)
- Guilt or feelings of worthlessness
- Energy loss (fatigue)
- Cognition/Concentration impairment
- Appetite changes (weight loss or gain)
- Psychomotor agitation or retardation
- Suicidal ideation
Clinical Approach
Diagnosis
- Clinical diagnosis based on DSM-5 criteria
- Must rule out medical causes (e.g., Hypothyroidism) and substance-induced mood disorders
- Must ensure there has NEVER been a manic or hypomanic episode (which would indicate Bipolar Disorder)
Management
- Pharmacotherapy: SSRIs (e.g., Sertraline, Fluoxetine, Escitalopram) are first-line. SNRIs, Bupropion, or Mirtazapine are alternatives.
- Psychotherapy: Cognitive Behavioral Therapy (CBT) or Interpersonal Therapy (IPT)
- Electroconvulsive Therapy (ECT): Highly effective for severe, refractory MDD, psychotic depression, or when rapid response is needed (e.g., active suicidality)
Complications
- Suicide
- Severe functional impairment (job loss, relationship breakdown)
- Increased risk of cardiovascular disease