Chunk #7 — Basic methodology of genetic epidemiology: an overview of twin studies — Principle 1: Genetic influences change in importance across adolescence
In the same way that alcohol use behavior shows dynamic change across the period of adolescence, twin studies demonstrate that the importance of genetic and environmental influences on alcohol use also change dramatically over this developmental period. Data from two population-based longitudinal Finnish twin studies illustrate the striking shift in the relative importance of genetic and environmental influences that occurs from early adolescence to young adulthood (Figure 1): there is a steady increase in the relevance of genetic factors on alcohol use across adolescence, and a corresponding and sharp decrease in the relevance of common environmental influences (Rose et al., 2001a; Rose et al., 2001b). These data demonstrate that while alcohol initiation is largely environmentally influenced, as has also been found in numerous other twin studies (Hopfer et al., 2003), as drinking patterns become more regular and established across adolescence, genetic factors assume increasing importance; however, alcohol use early in adolescence is influenced largely by family, school, and neighborhood factors (Rose et al., 2001b; Rose et al., 2003). A very similar pattern of results for alcohol use was obtained by
