Social support and protection from depression: systematic review of current findings in Western countries.

BACKGROUND Numerous studies report an association between social support and protection from depression, but no systematic review or meta-analysis exists on this topic. AIMS To review systematically the characteristics of social support (types and source) associated with protection from depression across life periods (childhood and adolescence; adulthood; older age) and by study design (cross-sectional v cohort studies). METHOD A systematic literature search conducted in February 2015 yielded 100 eligible studies. Study quality was assessed using a critical appraisal checklist, followed by meta-analyses. RESULTS Sources of support varied across life periods, with parental support being most important among children and adolescents, whereas adults and older adults relied more on spouses, followed by family and then friends. Significant heterogeneity in social support measurement was noted. Effects were weaker in both magnitude and significance in cohort studies. CONCLUSIONS Knowledge gaps remain due to social support measurement heterogeneity and to evidence of reverse causality bias.