A multi-level developmental approach towards understanding adolescent mental health and behaviour: rationale, design and methods of the LIFECOURSE study in Iceland.

Purpose: Identifying and understanding modifiable risk and protective factors that can inform early detection and intervention to prevent adolescent emotional problems and harmful behaviours is among the most pressing modern-day public health challenges. This paper describes the rationale, objectives, methods, and anticipated outcomes of the LIFECOURSE study, a multi-level, bio-psychosocial prospective study designed to advance our understanding of factors that shape adolescent mental health and behaviour.

Methods: Conducted by the Icelandic Centre for Social Research and Analysis at Reykjavik University, LIFECOURSE is a longitudinal population-based developmental study of Icelandic adolescents born in 2004. The study utilizes a comprehensive multi-informant assessment of individual, societal and biological factors measured across the lifespan. Data assembly and collection were conducted from 2016-2020 and utilize both retrospective and prospective data sources: (a) retrospective registry data assembled from seven national databases, (b) prospectively collected social surveys and (c) biomarker samples.

Results: Of the 3914 eligible adolescents, 60.8% (n = 2378) provided informed parental consent and student assent to participate in the study, with approximately half of the participants being female (n = 1175, 49.4%) and the majority being born in the capital area (n = 1455; 61.2%). The coverage of available data from the national databases and participation in the social surveys ranged from 81.7 to 100%.

Conclusions: Major gaps remain in our knowledge of how individual, societal and biological factors across the lifespan-from early life to adolescence-interact and shape the risk for emotional problems and harmful behaviours during adolescence. The LIFECOURSE study was designed to address this knowledge gap.