<p>This Perspective outlines developmental origins of mental health and disorders (DOMHaD) as a proposed theoretical framework, building on the concept of the developmental origins of health and disease (DOHaD). DOMHaD is supported by accumulating evidence that all major psychiatric disorders, including those with adult onset, have their origins in development, including neurodevelopmental trajectories and spatiotemporal regulation of brain–body interactions. DOMHaD incorporates the understanding that each individual’s genome, determined at conception, makes them predisposed or resilient to one or more disorders. Overlaid on these genetic factors are environmental and epigenetic factors with origins before conception, via parental exposures, and ongoing in utero, postnatal, childhood and adolescent exposures. These genetic and environmental factors interact over time, revealing healthy and dysfunctional developmental paths as two sides of the same complex ‘coin’. Implications of the DOMHaD conceptual framework for the understanding, prevention and treatment of psychiatric disorders are discussed.</p>