Purpose: The aim is to investigate the (1) longitudinal development in mental ill-health and wellbeing from ages 11 to 14, (2) predictors of changes in mental health outcomes, and (3) sex and reporter differences.
Method: Data are taken from 9553 participants in the Millennium Cohort Study, with both mental ill-health (parent- and self-report) and wellbeing outcomes of the cohort members measured at ages 11 and 14. A range of childhood socio-demographic, human capital, family and wider environment risk and protective factors are investigated.
Results: Wellbeing has weak stability and mental ill-health has moderate stability between ages 11 and 14 and large sex differences emerge in all the mental health outcomes investigated, with girls experiencing lower wellbeing and greater symptoms of mental illness at age 14. Raw associations between outcomes, and differences in their predictors, indicate varying patterns emerging for parent- and self-reported mental ill-health, with parent-reported symptoms in childhood a poor predictor of both self-reported wellbeing and depressive symptoms in adolescence. Investigating the emergent sex differences in prevalences highlights childhood risk and protective factors at this age that are more salient in females, including family income, school connectedness, cognitive ability, whereas peer relationships and bullying were equally relevant for mental health development in both males and females.
Conclusion: Low-moderate stability of mental health outcomes stresses the importance of the transition period for mental health, highlighting an intervention window at these ages for prevention. Socio-economic status is associated with mental health development in females but not in males at this age, highlighting a sex-specific vulnerability of deprivation associated with poorer mental health in adolescent females.
Keywords: Depression; Longitudinal; Mental illness; Transition; Well-being.