Parental wealth and mental disorders in Norway (2006-2023): a nationwide registry-based study of 1.4 million young people.

Background: Young people from families with low socioeconomic position have higher rates of mental disorders. However, wealth is underexamined despite large wealth inequity worldwide. Here, we aim to investigate the relationship between early life parental wealth and mental disorders in young Norwegians. Methods: We conducted a population study of associations between early-life parental wealth and 17 diagnostic categories of mental disorders in 1.4 M children (7-12), adolescents (13-18), and young adults (19-24) observed 2006-2023. Ranked parental socioeconomic indicators at age 0-6 (wealth, income, occupation, and education) and mental disorder diagnoses (ICD-10 and ICPC-2) were obtained from Norwegian Tax, Employment, Education, and Control and Payment of Health Reimbursements registries. Estimates were derived from mean prevalences, generalised estimating equations, and sibling comparison designs. Findings: Parental wealth represents a gradient in young people's mental disorders across age, sex, diagnostic categories, and cohorts. The lowest wealth quintile demonstrated 87% [95% CI = 78-96%] higher 1-year prevalence than the highest quintile. In multivariable analyses, parental wealth was the strongest predictor of mental disorders relative risk in adolescents (1.83 [1.76-1.9]) and young adults (1.92 [1.8-2.04]), while wealth (1.53 [1.46-1.6]) and education (1.52 [1.45-1.6]) were the strongest predictors in children. Parental wealth has a significant within-family association with mental disorders (relative risks: children 1.57 [1.44-1.71], adolescents 1.34 [1.26-1.42], young adults 1.42 [1.31-1.54]). Interpretation: Our study serves as a point of reference for understanding the relationship between parental wealth and mental health. Our findings establish early life parental wealth as a fundamental social gradient in young people's mental disorders. Funding: European Research Council consolidator grant (#101045526).