During this period, research established population-based estimates of DSM-based mental disorders in adults using large community samples, grounding the recognized burden in epidemiologic data. It underscored that many disorders originate in adolescence or young adulthood and that early onset forecasts greater risk for later substance use, underscoring the need for early detection and preventive strategies. Attention to homelessness with co-occurring disorders highlighted diagnostic complexity and the necessity for integrated, cross-system care, while growing attention to late-life mental health began shaping geriatric psychiatry research and policy discussions.