(HealthDay News) – Drug abuse in an adoptive home environment is a complex syndrome influenced by a range of genetic and environmental risk factors.

To investigate the genetic and familial environmental risk factors for drug abuse, Kenneth S. Kendler, MD, of the Virginia Institute for Psychiatric and Behavioral Genetics in Richmond, and colleagues conducted a national study in Sweden, including 18,115 adopted children, 78,079 biological parents and siblings, and 51,208 adoptive parents and siblings. Medical, legal, and pharmacy registry records were used to assess drug abuse.

The researchers found that there was a significantly higher drug abuse risk in adopted children of parents with drug abuse (odds ratio [OR], 2.09), in adoptive siblings of adopted children with drug abuse (OR, 1.95), and in biological full and half siblings of adopted children with drug abuse (OR, 1.84 and 1.41, respectively). The risk of drug abuse was strongly predicted by both genetic risk index (biological parental or sibling history, criminal activity, and psychiatric or alcohol problems) and environmental risk index (adoptive parental history of divorce, death, criminal activity, and alcohol problems, as well as adoptive sibling history of drug abuse and alcohol or psychiatric problems). A significant positive interaction was found for genetic and environmental risk indices in a model which included both indices together with gender and age of adoption.

“Adverse environmental effects on drug abuse are more pathogenic in individuals with high levels of genetic risk,” the authors write.

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