Depression

Description and Occurrence of Depression

[Page 556]The fifth edition of the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders provides the most recent description and classification of depressive disorders. The primary depressive disorders consist of major depressive disorder, persistent depressive disorder (formerly dysthymic disorder), and depressive disorder not otherwise specified. The depressive disorders comprise different groupings of symptoms that differ according to type, duration, severity, and resulting impairment. Major depressive disorder involves the consistent presence of depressed mood (or irritability in childhood and adolescence) or loss of interest in normal activities (i.e., anhedonia) for at least 2 weeks, accompanied by at least four additional symptoms, such as appetite or weight fluctuations, sleep disruptions, psychomotor disturbances, low energy or fatigue, and a variety of cognitive symptoms (e.g., worthlessness, difficulty concentrating or making decisions, suicidal ideation). Persistent depressive disorder is comprised of the consistent presence of depressed or irritable mood for at least 2 years (or 1 year in childhood and adolescence), accompanied by at least two additional symptoms such as appetite or sleep fluctuations, low energy or fatigue, or cognitive symptoms. Depressive disorder not otherwise specified includes constellations of depressive symptoms that do not fully meet diagnostic criteria for major depressive disorder or persistent depressive disorder due to an insufficient number, severity, or duration of symptoms.

Although the prevalence of diagnosable depression is relatively low during childhood (approximately 2–4%), a marked escalation in rates is observed during early-to-mid adolescence, particularly for girls, such that mid-to-late adolescent females experience depression at approximately twice the frequency of males. Elucidating the causal factors that contribute to the emergence of the sex difference in depression has been the focus of much research, which attributes this difference to the biological, psychological, and social sex-specific risks that females confront across the pubertal transition as well as enduring challenges for women across later life. Subsequent to this developmental shift, prevalence rates of clinical depression in mid-to-late adolescence are equivalent to those witnessed across adulthood (15–25%). However, subclinical levels of depressive symptoms occur in greater frequencies across all developmental stages. Beyond the impairment associated with discrete diagnosable episodes and subthreshold symptoms, depression is a disorder that tends to recur and to co-occur, or evince comorbidity, with other psychological disorders including anxiety, externalizing disorders, eating and substance use disorders, and personality disorders.

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