What is the relationship between individual and clusters of lifestyle behaviours during early adolescence on future youth mental health? A prospective cohort study

Aim: To analyze the gender stratified associations of individual and clustered unhealthy behaviors during early adolescence (i.e., 11 years) with internalizing and externalizing symptoms during mid- and late adolescence (i.e., 14 and 17 years).

Methods: We used data from the Millennium Cohort Study including 9127 (4642 girls) participants at 14 years of age and 6970 (3611 girls) at 17 years of age. Internalizing and externalizing symptoms were self-reported by the main caregiver using the Strengths and Difficulties Questionnaire at 11 years, 14 years, and 17 years. Depressive symptoms were estimated using the Mood and Feelings Questionnaire at 14 years. Psychological distress was assessed using the six-item Kessler psychological distress scale at 17 years. Unhealthy behaviors (i.e., low sports practice, elevated TV-viewing, daily soft drink consumption, < 2 portions/day of fruits, alcohol consumption and tobacco use) were assessed at 11years. We used negative binomial regression models, adjusting for potential confounders assessed at 11y.

Results: Clustering three or more unhealthy behaviors at 11 years was associated with higher depressive symptoms (Boys: incidence rate ratio, IRR: 1.35; 95% CI: 1.17–1.56; Girls: 1.23; 1.10–1.38) and peer problems (boys: 1.36; 1.17–1.56; girls: 1.22; 1.08–1.38) at 14 years in both genders, as well as emotional problems among boys. Similarly, clustering three or more unhealthy behaviors was associated with higher peer problems (boys: 1.33; 1.16–1.51; girls: 1.24; 1.08–1.42) and psychological distress (boys:1.14; 1.04–1.25; girls: 1.10; 1.02–1.30) at 17 years among both genders as well as emotional problems among boys. Despite the high prevalence emotional problems among girls in both waves, there was a linear trend of increasing risk of the outcome with the increase in the number of unhealthy behaviors. Low sports practice and TV viewing were the unhealthy behaviors most consistently associated with later mental health-related outcomes.

Conclusion: Clustering two or more unhealthy behaviors during early adolescence was associated with higher internalizing and depressive symptoms in mid-adolescence, as well as internalizing symptoms and psychological distress in late adolescence.