Objectives: Adolescent health behaviours are key determinants of long-term health. We aimed to explore the associations between clusters of families with similar socio-familial characteristics and health behaviours in both adolescents and their parents.

Study design: The design of the study is a cross-sectional analysis.

Methods: We enrolled adolescents aged 14-17 years and their parents from the SEROCoV-KIDS cohort study (December 2021-June 2022), based in the Canton of Geneva, Switzerland. Marginal logistic regressions were used to compute the sex- and age-adjusted prevalence differences (ΔaPrev) in smoking, alcohol and soda consumption, sport activity, unprotected intercourse, social media addiction, and adherence to COVID-19 vaccination guidelines between socio-familial clusters identified with K-means clustering (disadvantaged vs advantaged).

Results: Among 508 adolescents, two socio-familial clusters were identified: a disadvantaged group of 133 individuals characterised by lower socioeconomic status and social support, and an advantaged group of 375 individuals with more favourable socio-familial conditions. Adolescents in the disadvantaged cluster had a significantly higher prevalence of smoking (ΔaPrev 7.4 %; 95 % CI: 1.1; 14.1), daily soda consumption (ΔaPrev 12.9 %; 95 % CI: 2.6; 23.2), reduced sport activity, and lower adherence to COVID-19 vaccination guidelines. Similar patterns were observed among parents. No differences were found in alcohol use, social media addiction, or unprotected intercourse.

Conclusion: Large disparities in health behaviours associated with socio-familial environments emerge early in adolescence. It is crucial to adopt a holistic health strategy that recognises the interplay between socio-demographic context, family dynamics, and health behaviours.