Besides direct risk enhancing or buffering effects on substance use, we hypothesize that these parenting factors moderate the importance of genetic check details influences on regular alcohol and cannabis use. In other words, we expect that parental rejection, overprotection and emotional warmth have an overall influence on an adolescents’ risk of regular substance use, but also that adolescent carriers of the genetic risk markers in DRD2 and DRD4 are most vulnerable to the influence of less optimal parenting manifested

in a higher likelihood of regular substance use. Related gene by parenting interactions have been identified with respect to adolescent substance use (Dick et al., 2007 and van der Zwaluw et al., 2009), indicating that a genetic liability increases the likelihood of substance use or abuse only when specific parenting styles are applied. With regard to the DRD2 TaqIA polymorphism, findings

by van der Zwaluw and co-workers show that adolescents carrying the A1 allele AND who have parents that are highly permissive towards alcohol consumption, use significantly more alcohol selleck products over time than adolescents without these characteristics (van der Zwaluw et al., 2009). We do not know of any studies that investigated DRD4 by parenting interactions in relation to adolescent substance use. Moreover, it remains undetermined if general parenting also affects the actual expression of a genetic predisposition to regular alcohol use, and if gene by parenting interactions are also applicable to adolescent cannabis use. Using data from the Tracking Adolescents’ Individual Lives Vasopressin Receptor Survey (TRAILS), a large, general population sample of Dutch adolescents, we have tested (1) for direct effects of DRD2 and DRD4 polymorphisms on alcohol and cannabis use, and (2) whether parenting modifies the expression of a genetic liability for alcohol and cannabis use. The focus of the present

study is on regular patterns of alcohol and cannabis use in young adolescents, enabling us to get more insight in specific subgroups of alcohol and cannabis users that have a high risk of adverse outcomes. The present study reports data from the first (T1) and third (T3) assessments of TRAILS, which ran from 2001 to 2002, and from 2005 to 2007, respectively. A detailed description of the sampling procedure and methods is provided in de Winter et al. (2005) and Huisman et al. (2008). Briefly, the TRAILS target sample involved all 10–11-year-old children living in five municipalities in the North of the Netherlands, including both urban and rural areas. Seventy-six percent of the target population (n = 2230, mean age = 11.09, SD = 0.55, 50.8% girls) was enrolled in the study (i.e., both child and parent agreed to participate).