Tracking the associations between environmental factors and structural connectivity changes in adolescence.

Introduction: Adolescence is a dynamic period of brain development, with important influences from a range of environmental factors, with combined impacts on trajectories of mental health and wellbeing. Various brain regions that process cognitive and social information develop throughout adolescence, and the way these regions interact is critical, as young people learn to navigate their increasingly social and independent lives. Described as ‘structural connectivity’, white matter (WM) projections play a vital role in linking neural elements within brain regions and serve to optimise the efficiency of information processing. Since 2018, the Longitudinal Adolescent Brain Study (LABS) has frequently assessed numerous measures of mental health & wellbeing, as well as a range of lifestyle and environmental factors, in conjunction with neuroimaging, as participants progress through adolescence. LABS researchers have been investigating the relationships between changes in WM integrity (as measured via diffusion tensor imaging; DTI) and a range of environmental factors. Methods: Data is collected from LABS participants, from 12 years-of-age, at 4-month intervals, over a 5-year period. At each time-point, data collection involves self-report questionnaires, cognitive assessments, neuropsychiatric interview, electroencephalography and neuroimaging (including DTI). To date, 180 adolescents have commenced LABS, with 1000+ assessments completed (up to 15 timepoints for some individuals). Structural connectivity from DTI, is indexed by WM integrity measures (fractional anisotropy [FA], axial diffusivity [AD], radial diffusivity [RD]) from projection, commissural and association fibre pathways (tracts). Across our studies, cohort-specific templates are utilised as the target of the tract-based spatial statistics analysis (TBSS). Environmental/lifestyle factors such as sleep quality, social connectedness and screen time/social media use is recorded via self-report, whereas childhood adversity is recorded via interview with a clinical psychologist, when participants reach 16 years of age; they are asked about any early life stress or traumatic events that they may have experienced. Results: A series of papers/analyses that involve the tracking of WM profiles (FA, AD, RD) during adolescent development, and their associations with mental health and well-being outcomes, as well as environmental factors (sleep quality, social connectedness or early life stress/childhood adversity) will be presented. More specially, development trajectories of WM diffusion metrics utilise generalised estimated equations or generalised additive mixed modelling and incorporate potentially differentiating factors such as biological sex and socio-economic status. Conclusions: LABS has great scope to identify the links between structural brain changes and environmental factors as young people progress through adolescence, with potential fluctuations in their mental health and wellbeing. It is important to understand the mechanisms involved in the maturation of structural connectivity, particularly between functional brain regions implicated in the processing of complex cognitive and social information, and how these impact or influence adolescents’ mental health and wellbeing.