Adopted children whose biological parents abused drugs are twice as likely to do so themselves, compared with adopted children whose birth parents did not abuse drugs, a new study finds.
The study of more than 18,000 adopted children in Sweden found substance abuse in a child’s adoptive family also is a risk factor, suggesting both environment and genetics can play a role in a child’s risk of future drug use, CNN reports. The study found that children with an adoptive sibling who develops a drug abuse problem also have a doubled risk of drug abuse.
“For someone at low genetic risk, being in a bad environment conveys only a modestly increased risk of drug abuse,” lead study author Dr. Kenneth S. Kendler of Virginia Commonwealth University in Richmond said. “But if you are at high genetic risk, this can put your risk for drug abuse much higher.”
In a news release, the researchers point out, “Relatives that share genes and environment make it difficult to determine if the family dysfunction is linked to the drug abuse or if it is genetics at play. There have been no large-scale adoption studies performed to verify the findings, until now.”
The study found 4.5 percent of adopted individuals had problems with drug abuse, compared with 2.9 percent of the general population. Among those who had at least one biological parent who abused drugs, 8.6 percent had their own drug abuse problems, compared with 4.2 percent of those whose biological parents did not have drug abuse issues.
Adopted children had about twice the risk of drug abuse if either their biological full or half-sibling had a drug abuse problem, or if their adoptive siblings had abused drugs, the article notes.
The study appears in the Archives of General Psychiatry.