Child-To-Adult Body Size Change and Risk of Depression and Anxiety: A Large Prospective Cohort Study.

BACKGROUND: Body size across the life course has been associated with long-term mental health outcomes, yet most previous studies have examined body size at a single developmental stage. Whether changes in relative body size from childhood to adulthood represent a distinct life-course marker of vulnerability to later depression and anxiety remains insufficiently understood. We examined the associations between child-to-adult body size changes and the risk of depression and anxiety and explored whether lifestyle factors and chronic diseases partly explained these associations. METHODS: This study included 447,821 participants from the UK Biobank. Childhood body size at age 10 years was retrospectively self-reported as relative body size, and adult body size was assessed using measured body mass index (BMI) at baseline. Depression and anxiety were identified from electronic health records questionnaires, including the Patient Health Questionnaire-9 and the Generalized Anxiety Disorder-7. Cox proportional hazards models were used to estimate associations with incident diagnoses, and mixed-effects linear regression models were used to examine symptom severity scores. Exploratory mediation analyses were conducted to assess the extent to which lifestyle factors and chronic diseases, including type 2 diabetes (T2D), hypertension and cardiovascular disease (CVD), statistically accounted for the observed associations. RESULTS: In the fully adjusted models, childLow-adultHigh group had the highest risk of major depression (HR: 1.90, 95% CI: 1.79-2.01) and anxiety (HR: 1.58, 95% CI: 1.48-1.68) compared with the childAverage-adultAverage group. Unhealthy lifestyle factors and chronic diseases together statistically accounted for 21.9% of the association between the childLow-adultHigh group and major depression and 22.2% of the association between the childLow-adultHigh group and anxiety. CONCLUSIONS: Distinct body size changes from childhood to adulthood are associated with differential risks of depression and anxiety. Individuals transitioning from childhood leanness to adult heaviness may represent a particularly vulnerable life-course group. These findings support the importance of life-course approaches to understanding mental health vulnerability and identifying opportunities for early prevention.