Chapter 13: Mood Disorders

The material traces the conceptual development from classical descriptions of melancholia through Kraepelinian nosology to current diagnostic frameworks, establishing how mood disorders are classified and distinguished in the DSM-5-TR and ICD-11. Major depressive disorder, persistent depressive disorder, disruptive mood dysregulation disorder, bipolar I and II disorders, and cyclothymic disorder are examined through their defining features, including disturbances in mood valence, anhedonia, neurovegetative symptoms, psychomotor changes, and cognitive impairment. The chapter emphasizes epidemiological patterns, documenting lifetime prevalence rates, gender disparities in depression incidence, and the substantial overlap between mood disorders and comorbid anxiety, substance use, and medical conditions. Biological mechanisms are explored through neuroendocrine dysfunction, circadian rhythm perturbations, monoamine neurotransmitter dysregulation, and neuroimaging evidence revealing structural and functional brain abnormalities in key limbic and prefrontal regions. Etiological understanding integrates genetic vulnerability, developmental trauma, personality factors, and psychosocial stressors into biopsychosocial models of illness onset. The chapter details the longitudinal course of these conditions, including recurrence patterns in major depression and cycling characteristics in bipolar illness, alongside prognostic factors influencing treatment response and chronicity. Pharmacological interventions including antidepressants, lithium carbonate, anticonvulsant mood stabilizers, and antipsychotics are reviewed with emphasis on mechanism of action and efficacy data. Evidence-based psychotherapeutic approaches such as cognitive-behavioral therapy, interpersonal therapy, and family-focused interventions are integrated with somatic treatments including electroconvulsive therapy, transcranial magnetic stimulation, and emerging options like ketamine and esketamine. Treatment-resistant depression receives detailed attention with discussion of augmentation strategies and novel approaches. The chapter concludes by addressing cultural variation in mood disorder presentation, global disease burden, and comprehensive suicide prevention frameworks, reinforcing that mood disorders represent highly prevalent yet substantially treatable conditions when managed through integrated multimodal care.