The impact of positive experiences in childhood and adolescence on later mental health: A systematic review of longitudinal cohort studies

Background Positive experiences in early life are increasingly recognised as important contributors to mental health across the lifespan. While adverse childhood experiences have been extensively studied, the role of singular and cumulative positive experiences remains less well understood. This systematic review synthesises longitudinal evidence on associations between empirically measured positive experiences in childhood or adolescence and adult mental health outcomes. Methods Four databases (APA PsycInfo, Embase, MEDLINE, and Scopus) were searched from inception to January 2024 and updated in May 2026. Eligible studies were longitudinal cohort studies examining associations between exposure to singular or cumulative positive experiences from birth to age 18 and adult outcomes of depression, anxiety, psychosis, or bipolar disorder, measured through clinical diagnoses, symptom‐level assessments, or broader psychopathology indices. Risk of bias was assessed using the Joanna Briggs Institute Critical Appraisal Checklist, and findings were narratively synthesised. The protocol was registered on PROSPERO (CRD42023482969). Results 20 studies ( N = 63,271) were included. Physical activity, engaged parenting, peer social support, school belonging, school connectedness, religious service attendance, and cumulative positive experiences were associated with a reduced risk of adult depression. School belonging, school connectedness, perceived support from family and friends, and a greater number of positive relative to adverse experiences were associated with lower levels of anxiety. A positive home atmosphere, greater social cohesion, higher levels of physical and leisure‐time activity, and participation in sports competitions were linked to fewer psychotic symptoms. No studies examined bipolar disorder. All studies were of moderate to high quality, although definitions and measurement of positive experiences varied. Conclusion Positive experiences in childhood and adolescence may contribute to better mental health outcomes in adulthood. However, further longitudinal research is needed to clarify mechanisms, timing, and cumulative effects, and to standardise measurement across diverse populations.