Chunk #15 — Basic methodology of genetic epidemiology: an overview of twin studies — Principle 3: The environment moderates the importance of genetic influences
impacting adolescent smoking, whereas in homes with very high parental monitoring, genetic effects played little to no role, and common environmental factors were the most important influence (Dick et al., 2007b). Similar effects have been demonstrated for more general externalizing behavior: genetic influences on antisocial behavior were higher in the presence of delinquent peers (Button et al., 2007) and in environments characterized by high parental negativity (Feinberg et al., 2007), low parental warmth (Feinberg et al., 2007), high paternal punitive discipline (Button et al., 2008), and environmental adversity more generally (Hicks et al., 2009). Socioregional, or neighborhood-level influences have also been shown to moderate the importance of genetic influences on substance use. Genetic influences on late adolescent alcohol use and early adolescent behavior problems are enhanced in urban environments, communities characterized by greater migration, and neighborhoods with higher percentages of slightly older adolescents/young adults (Dick et al., 2009a; Dick et al., 2001; Rose et al., 2001a). These moderation effects presumably reflect differences in availability of alcohol, a range of possible different role models, neighborhood stability, and community-level monitoring across different areas. The environments for which there are demonstrated moderating effects on genetic influences in adolescence largely appear to reflect differential
