The ROOTS study: a 10-year review of findings on adolescent depression, and recommendations for future longitudinal research

PURPOSE: The purpose of this study is to review longitudinal findings on adolescent mental health from the ‘ROOTS study’, and provide directions and recommendations for future longitudinal research. To do this, we discuss relevant findings from the ROOTS study, and review its strengths and limitations. METHODS: We examined all publications from the ROOTS study up to July 2015, selected those examining adolescent mental health, and classified them as investigating (a) childhood risk factors for adolescent depression, (b) genetic and cognitive vulnerability to depression in adolescence, (c) genetic markers, childhood adversities, and neuroendophenotypes, (d) morning cortisol and depression, (e) physical activity and depression symptoms, and (f) the underlying structure of mental health in adolescence. We reviewed the strengths and limitations of the ROOTS study, and how they feed into recommendations for future longitudinal research. RESULTS: There was evidence supporting a putative hormonal biomarker for the emergence of depression in boys. Environmental pathways from child adversity to adolescent depression were confirmed in girls, partly accounted for by negative life events in early adolescence. The preceding role of automatic cognitive biases assessed using behavioural tasks was substantiated, with evidence for genetic susceptibility. Novel latent statistical models of child adversity, depression, anxiety, and psychotic experiences were produced, with concurrent and prospective validity. Our experiences conducting the ROOTS study resulted in a set of strengths, limitations, and recommendations for future longitudinal studies. CONCLUSIONS: The ROOTS study has advanced knowledge on the aetiology of adolescent depression by investigating environmental, genetic, hormonal, and neural risk factors. Findings provide a foundation for future research integrating cognitive neuroscience with epidemiology.