RecruitingBehavioural interventionAdolescent Mood During Puberty and TestosteroneStarting at puberty, female adolescents are nearly three-times more likely to develop internalizing disorders, like depression, while male adolescents are two-times more likely to develop externalizing disorders, like attention deficit hyperactivity disorder (ADHD). This divergence between the sexes during puberty suggests sex-specific pathways of risk and differential effects of sex hormones. The purpose of this research is to determine: 1) sex-specific neural and endocrine features of the pubertal transition that may mediate sex differences in adolescent mood disorders, and 2) the neurophysiological basis of susceptibility to hormone change during puberty.