In the past few decades, hundreds of controlled studies have examined the effects of mental health programs aimed at preventing mental health problems at school, work-related stress, distress among caregivers for the elderly, and many other conditions.

This considerable body of research has shown that some prevention programs in mental health are capable of strengthening protective factors, such as social skills, problem-solving skills, stress-management skills, pro-social behavior, and social support; that these programs can reduce the consequences of risk factors and psychiatric symptoms; and that they may have positive economic effects.
Despite this large body of research, relatively few studies have examined whether these prevention programs are actually capable of reducing the incidence of new cases of major depression or other mental disorders defined according to diagnostic criteria.However, in the past two decades a growing number of randomized trials have examined whether it is possible to prevent the onset of depressive disorders.