Major Depressive Disorder (Single Episode)

Major depressive disorder (MDD), single episode is a mood disorder characterized by the presence of one discrete episode of major depression, lasting at least two weeks, with significant impairment in social, occupational, or educational functioning. Etiologies involve complex interactions between genetic vulnerability, neurotransmitter dysregulation (serotonin, norepinephrine, dopamine), hormonal imbalances, and psychosocial stressors. Clinical features include persistent low mood, anhedonia, fatigue, changes in appetite or sleep, psychomotor changes, and recurrent thoughts of death or suicidal ideation. Diagnosis is based on DSM-5 or ICD-11 criteria and requires exclusion of substance-induced mood disorders or mood disturbances secondary to medical conditions. Management typically includes psychotherapy (cognitive-behavioral therapy or interpersonal therapy), pharmacotherapy (SSRIs, SNRIs, or atypical antidepressants), and, in severe cases, electroconvulsive therapy, with prognosis improved by early and comprehensive intervention.