The pathways that lead to associations between religious attendance and alcohol involvement may involve shared familial factors (eg, genetic attributes or shared environment that predisposes youth to prosocial behaviors) as well as individual-specific environmental factors that influence both religiosity and alcohol involvement (eg, an experience of trauma that leads to decreased religiosity as well as increased alcohol use). Twin studies offer an ideal approach for disentangling the role of genetic and environmental influences on the covariance between religious service attendance and alcohol involvement. These studies suggest that genetic and shared environmental factors contribute to familial sources of resemblance in earlier and non-problem stages of alcohol use (eg, regular drinking), while genetic factors are more distinctly important for problem drinking.19 On the other hand, the role of shared environment has been more frequently implicated in studies of religiosity (variously defined, eg, ref.4,20–22), even though its role declines from adolescence to adulthood, being replaced by genetic factors.23,24 Two studies explored whether religiosity modified the extent to which genetic factors influence alcohol use. Koopmans et al.25 reported that while religiosity was not associated
