A robust finding to emerge from twin studies in the area of alcohol use in recent years is that genetic influences on alcohol use and related problems are dynamic. Throughout this section when I refer to genetic effects, I am referring to aggregate genetic influence, as inferred from twin comparisons, not effects associated with any specific gene. Twin studies indicate that genetic influences change across time, becoming increasingly important as individuals move from early adolescent experimentation to more established patterns of alcohol use later in adolescence/emerging adulthood (Rose, Dick, Viken, & Kaprio, 2001), and they can also change profoundly as a function of the environment. In the Finnish twin studies, we have initiated a program of research aimed at identifying environmental factors that modify the relative importance of genetic and environmental influences on alcohol related outcomes across development. We have found that environments across a number of different domains can play important roles in moderating the importance of genetic effects. Initially we found that a number of different socioregional factors moderated the relative importance of genetic and environmental effects. Genetic
