From environment to genes and back to the environment

This overview paper summarizes the results of studies that were conducted in the framework of two interdisciplinary, longitudinal projects of which Luc Goossens was a principal investigator: Studying the Transition to Adolescence: Testing Genes, Interactions, and Environments (STRATEGIES), and Methylation and Internalizing Problem Behaviors in Adolescence: Examining Associations Across Multiple Levels of Analysis (MIND). The main aim of these projects was to investigate to which extent genes as personal characteristics, in interaction with different environments (family, teachers and peers), can affect developmental outcomes in adolescents, such as internalizing and externalizing behaviours, loneliness, and school engagement. Different approaches were used to include genetic information, such as single nucleotide polymorphisms, polygenic scores, and methylation, and specific statistical methods were applied to combine genetic information. Although no strong conclusions could be made about GxE interactions, there is evidence for the contribution of parents, teachers and peers (in the development) of adolescent behaviours and emotions, but genes also appear to play a role.