Chapter 69: Mood Disorders

Major depressive disorder is characterized by persistent depressed mood and anhedonia, with lifetime prevalence of approximately 8.4% among U.S. adults and higher incidence in females and young adults aged 18 to 25. The underlying pathophysiology involves dysregulation of monoamine neurotransmitters including serotonin, norepinephrine, and dopamine, alongside structural brain changes such as hippocampal volume reduction and elevated amygdala reactivity, with strong genetic contributions evidenced by twin studies. Assessment relies on validated screening instruments including the PHQ-2 for initial detection and the PHQ-9 for diagnostic confirmation and symptom monitoring, supplemented by specialized tools for geriatric and postpartum populations. First-line pharmacological interventions include selective serotonin reuptake inhibitors, serotonin-norepinephrine reuptake inhibitors, and norepinephrine-dopamine reuptake inhibitors, requiring careful monitoring for adverse effects and the black box warning for increased suicidality in younger patients. Cognitive behavioral therapy and interpersonal psychotherapy demonstrate effectiveness particularly when integrated with medication management. Bipolar and related disorders present a distinct clinical challenge involving cyclical mood episodes ranging from mania to depression, with three primary classifications determined by episode duration and severity. The diagnostic confusion between bipolar disorder and major depressive disorder carries serious clinical implications, as antidepressant monotherapy can precipitate manic episodes. Lithium remains the gold standard mood stabilizer with unique antisuicidal properties, while alternative treatments include valproic acid, anticonvulsants, and second-generation antipsychotics. Suicide assessment represents a critical competency requiring knowledge of validated risk evaluation tools and identification of high-risk populations including veterans, older males, and LGBTQ plus individuals, with evidence indicating that previous suicide attempts constitute the strongest predictor of future risk. Management strategies encompass acute interventions such as hospitalization for imminent risk alongside longer-term safety planning and community-based prevention efforts.