Peer problems and prosocial behaviours across development: Associations with anxiety and depression in emerging adulthood

Peer problems in childhood and adolescence are associated with anxiety and depression in emerging adulthood. However, it remains unclear whether prosocial behaviours reduce this risk and whether these associations remain after adjusting for familial factors, including genetics. The present study examined how the development of peer problems and prosocial behaviours across childhood and adolescence were associated with anxiety and depression in emerging adulthood, and whether these associations remained when using a monozygotic twin difference design. The study included up to 31,016 participants (50.4 % female) from the Twins Early Development Study (TEDS; N = 19,758) and the Avon Longitudinal Study of Parents and Children (ALSPAC; N = 11,258), with sample sizes varying across analyses based on data availability. Repeated data were collected from ages 4 to 26/28 (TEDS/ALSPAC). Results from latent growth curve and path analyses showed that higher initial levels of peer problems and prosocial behaviours in childhood, as well as more persistent peer problems and prosocial behaviours during childhood, increased risk for anxiety and depression in emerging adulthood. Associations with peer problems remained significant after adjusting for familial factors using monozygotic twin difference scores, suggesting that individual-specific experiences, like children's responses to peer problems, may explain why peer problems increase risk for later anxiety and depression. In contrast, associations with prosocial behaviours did not remain significant after adjusting for familial factors, indicating that whilst prosocial behaviours in childhood were associated with higher levels of anxiety and depression in emerging adulthood, this was largely explained by genetic or environmental factors shared within the family.