What are the effects of preventative interventions on major depressive disorder (MDD) in young adults? A systematic review and meta-analysis of randomized controlled trials

Background: Depression is a prevalent disorder with a peak rate of onset in young adulthood from 18 to 25 years. To date, no review has systematically assessed the effectiveness of programs that aim to reduce depressive symptoms or diagnosis of depression in young adults.

Method: A systematic search was performed in Cochrane, PubMed, PsycINFO and EMBASE. We performed a random-effects meta-analysis of the randomized controlled studies that compared an intervention for young adults (aged 18-25) without a diagnosis or history of depression and a control condition. Comparisons between intervention and control group outcomes were carried out at the post-intervention time point. We also compared intervention and control group outcomes at later follow-up time points where data were available.

Results: Twenty-six randomized controlled trials among 2865 young adults were included in the analysis. The pooled effect size of the interventions versus control at post-intervention was g = 0.37 (95% CI: 0.28-0.47, NNT = 9) and heterogeneity was moderate I² = 36 (95% CI: 11-64). There were no significant effects in terms of the type of delivery, focus of study, type of control, or type of support within the interventions.

Limitations: The authors were unable to assess the effects of interventions on the onset of depression as none of the included studies measured incidence. The risk of bias was high in most studies (81%). Only one study included a follow-up of more than a year. Demographic factors were inconsistently reported in the included articles.

Conclusion: While it was not possible to investigate the effects of interventions on depression incidence, some evidence was found for the effectiveness of preventative interventions in reducing depressive symptoms in young adults. Future research should address limitations of the current evidence base to allow stronger conclusions to be drawn.