REACH is an accelerated cohort study of adolescent mental health in two inner city London boroughs, Lambeth and Southwark. The study aims to investigate the impact of social, psychological, and biological risk and protective factors on the occurrence and persistence of mental health problems over time in large, ethnically diverse cohorts of adolescents.

REACH has recruited three cohorts—age 11–12 (cohort 1 school year 7), 12–13 (cohort 2 year 8) and 13–14 (cohort 3 year 9) from 12 mainstream secondary schools in the two boroughs. These boroughs are among the most densely-populated, socioeconomically and ethnically diverse areas in England, 13–15 and have high rates of adult mental health problems. To investigate novel questions on the developmental origins of mental health problems in adolescents, extensive data is collected at each time point. Participants provide detailed information, each year, about their mental health, social circumstances, and experiences via questionnaires. A subset (approx. 20%) of participants also complete face-to-face interviews and cognitive assessments.