Chunk #17 — Basic methodology of genetic epidemiology: an overview of twin studies — Principle 3: The environment moderates the importance of genetic influences
Further, it is likely that the importance of different environments as moderators of genetic effects varies across developmental stage. There is some indication of this in the Finnish twin data, where parental monitoring showed significant moderating effects on substance use starting earlier in adolescence (age 14), whereas the moderating role of peer substance use was not apparent until later in adolescence (age 17; Dick et al., 2007a). Similarly, socio-regional influences that moderated alcohol use in young adulthood did not show evidence of moderation of early adolescent alcohol use (Dick et al., 2009a). Accordingly, studying genetic influences on adolescent behavior illustrates that genetic factors can only be understood in the context of the environment, and that these interactions can also shift across developmental stage.
