The RADAR Young study (RADAR-Y) is a population-based prospective cohort study in which adolescents are followed from age 12 to 18 years. RADAR-Y focuses on the development of (1) adolescent parent and peer relationships, (2) personality and identity, (3) psychopathology and delinquency, (4) substance use, and (5) academic achievement. RADAR-Y has a full family design: 497 adolescents, their parents, a sibling and a friend participate. Families are followed for six years. Each year a full family assessment and three internet assessments (3 month interval) are conducted. All family members and the friend participate in the full family assessment. In the internet assessments the adolescent, the mother, and friend fill out questionnaire data during five consecutive days within one week. Outcome data are collected at each assessment. Additionally, reciprocal reports on family relationships (round robin design) are collected from all family members at each annual assessment. During internet assessments, data on relationship quality are collected each day. In addition, a subsample participated in a lab assessment including (among other things) the Public Speaking Task and Facial Empathy Task. This assessment took place around the fifth annual wave.

Keywords: Adolescence, personality, identity, psychopathology, substance use, delinquency, full family, friends

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