Randomised controlled trials (RCTs) evaluating the effects of a preventive intervention for depressive disorders compared with a no-treatment control group were eligible for inclusion. Eligible trials had to use a standardized diagnostic interview at baseline. Trials were also included that evaluated interventions aimed at reducing depressive disorders as a consequence of specific events (such as postnatal depression or post stroke depression) and did not have a pre-test assessment of depressive disorders, but reported a post-test assessment. Trials explicitly reporting including subjects with depressive disorders who received an intervention were excluded. The primary outcome of interest was the incidence of new cases of depressive disorders.
Intervention types included universal prevention (such as school programs and mass media campaigns aimed at the general population), individual programs aimed at high risk groups, and those aimed at individuals who have some symptoms of a mental disorder but did not meet the diagnostic criteria. Interventions included cognitive behavioural therapy, interpersonal psychotherapy/psycho-education, problem solving therapy, and debriefing compared with usual care. The majority of interventions were targeted at adults, but some interventions targeted adolescents. Participants in the included trials were pregnant women, mothers of pre-term babies, primiparous women, primary care patients, and students.
The authors did not state how papers were selected for the review, or how many reviewers conducted the selection.