Religiosity, a term used to describe multiple related constructs such as religious beliefs, religious values, and religious behavior, is a protective factor for alcohol use (Heath et al. 1999; Winter et al. 2002), and has also been shown to moderate the genetic influence on alcohol use initiation, particularly in females. In a study of 1967 Dutch twin pairs 12–26 years of age, genetic influences on initiation of alcohol use were attenuated in participants from religious backgrounds, compared with non-religious backgrounds (Koopmans et al. 1999). For individuals without a religious upbringing, heritability estimates of 40% and 39% were reported for males and females, respectively; for individuals with a religious upbringing heritability was estimated at 25% and 0% for males and females, respectively. Similar findings have also been reported for the influence of religiosity on the heritability of behavioral disinhibition (Boomsma et al. 1999), smoking initiation (Timberlake et al. 2006), and neuroticism (Willemsen and Boomsma 2007). In all of these studies, heritability estimates were lower in populations with a religious upbringing or self described religiousness. These findings are consistent with Heath and colleagues (1999) theory that genetic influences on behavioral outcomes are attenuated in environments where individuals' choices are more limited.
