The effects are particularly salient for girls. By their 19th birthday, 11 per cent of girls around the world are already mothers (WHO, 2016), while 27 per cent are married by age 18 (UNICEF, 2014). Adolescent girls and young women are one of the groups most severely affected by HIV (UNAIDS, 2014) and although gender gaps in access to primary education are closing, girls continue to be disadvantaged (UNESCO, 2015).These outcomes call for a strong focus on adolescent well-being in policies and programmes and are supported by a growing body of literature that recognizes adolescence as a critical phase for achieving human potential (Patton et al.,