The impact of positive childhood experiences on adult psychiatric disorder and symptoms: Protocol for a systematic review and meta-analysis of longitudinal cohort studies

Background Mental and substance use disorders are the leading cause of disability among young people worldwide. Early life environments and experiences have a significant influence on development with long-lasting implications for both physical and mental health. While the harmful effects of childhood adversity are well-documented, positive childhood experiences are less well-established and the degree of association with later mental health outcomes is currently undefined. The proposed systematic review will therefore examine the literature exploring associations between exposure to positive childhood experiences and the development of psychiatric disorder or symptoms in adulthood. Methods and analysis Studies examining associations between exposure to positive childhood experiences and risk of adult psychiatric disorder or symptoms will be systematically identified by searching Embase, APA PsycInfo, MEDLINE, and Scopus. Customised search strategies will be built for each database by combining key search terms relating to inclusion criteria. No restrictions on publication date will be applied, however searches will be restricted to the English language. Provided data are sufficient, a random-effects model at the 0.05 level of significance will be used to pool quantitative effect estimates. If meta-analysis is not possible, results will be summarised in tables and reported narratively. The Joanna Briggs Institute Critical Appraisal Checklist for Cohort Studies will be used for quality assessment of included studies and the overall strength of the body of evidence will be assessed using the Grading of Recommendations Assessment, Development, and Evaluation framework. Heterogeneity between included studies will be explored through visual inspection of forest plots and by assessing the I2 statistic. Reporting of this protocol has been guided by the standards of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols Statement. Ethics and dissemination Only published data will be used for this review therefore ethical approval is not required. Findings will be disseminated in a scientific peer-reviewed journal and results presented at conferences.