The genetic link between violence and alcoholism

Recent molecular genetic studies have suggested the possibility that alcoholism and violent behavior, two outcomes which are found to aggregate within individuals and within families may share a common gene. Only one epidemiological study, however, has reported a genetic relationship between alcoholism and violent behavior. In addition, the genetic and environmental factors involved in the co-occurrence of violent behavior and alcoholism are not well understood. Females, due to their lower levels of violent offending and low rate of alcoholism, have typically been omitted from analyses. The current study utilizes an adoption design, viewed as the most powerful epidemiological tool in addressing questions of nature versus nurture. Criminal and alcohol records were ascertained from a search of the Danish national registers. Within the context of the Danish Adoption Project (N = 14,427), the current study found that among the male adoptees, (1) biological parental violence was related to adopted-away offspring severe alcohol-related problems, via a mediational model; (2) severe alcohol-related problems in the biological parents was related to violence in the adopted-away offspring; and (3) these genetic factors interacted with specific environmental factors, such as adoptive parental lower socioeconomic status, to produce an elevated risk for negative outcomes among the adoptees. The relationship between biological parental violence and adopted-away male severe alcohol-related problems was significantly reduced if the adoptees were raised in a mid to high SES home. Some gender differences were observed. Biological parental violence was associated with elevated rates of severe alcoholism among the female adoptees; this represented a direct relationship. Biological parental severe alcohol-related problems was not found to be related to violent offending in the female adoptees, an outcome which may be attributed to the low rate of violent offending among females in general. Additionally, females did not inherit a greater genetic vulnerability towards criminal and alcohol problems than males. Overall, these findings support the hypothesis that violence and alcoholism share a common genetic basis. These findings also point to the importance of evaluating genetic and environmental factors in the ontogenesis of alcoholism and violence.