VCU news

By Anne Dreyfuss
C. Kenneth and Dianne Wright Center for Clinical and Translational Research

Pregnancy substantially reduces drug abuse risk, according to a new study conducted by researchers at Virginia Commonwealth University and Lund University in Sweden.

The study, titled “The Protective Effect of Pregnancy on Risk for Drug Abuse: A Population, Co-Relative, Co-Spouse, and Within-Individual Analysis,” published recently in the American Journal of Psychiatry. In the study, researchers found strong causal associations between pregnancy and subsequent reductions in drug abuse among pregnant women.

The results extend beyond the population parameters of pregnant women, implying that human volition plays an important role in drug abuse cessation and challenging a conventional wisdom that assigns drug abuse largely to biological factors.

“We have a couple models in the field of psychiatry about what causes drug abuse,” said first author Kenneth S. Kendler, M.D., professor of psychiatry and human and molecular genetics in the Department of Psychiatry at VCU School of Medicine. Kendler believes recent trends in psychiatry have assigned more importance to biological factors than to human volition. “Drug abuse is complicated, but human motivations under some circumstances can be potent at reducing the risk of drug abuse,” he said. “The findings from this study suggest that if you motivate people enough in ways that are important to them, they will be able to substantially lower their drug abuse risk.”

Using Swedish medical, criminal and pharmacy registries, researchers identified nearly 150,000 Swedish women who were born between 1980 and 1990, and gave birth between ages 20 and 35. Of those women, approximately 3,800 had a history of drug abuse. A portion of the sample included identical twins.

Researchers first examined women’s risk for drug abuse at different periods of life: prior to pregnancy, during pregnancy, and for about two years after giving birth. Compared with the immediately preceding equivalent time period, rates of drug abuse declined 78 percent during pregnancy. Similarly strong protective effects were found to extend two years postpartum, with rates of drug abuse similar to that seen in pregnancy.

“The protective effect of pregnancy is just as strong in mothers of newborns as it is when they are pregnant,” Kendler said.

Researchers also examined rates of drug abuse between identical twin sisters when one was pregnant and the other was not. They were able to predict an 83-percent reduced risk for drug abuse in a pregnant woman compared with her nonpregnant twin sister.

“Both scenarios produce the same results, which is about an 80 percent reduced risk for drug abuse,” Kendler said. “That is a huge effect.”

Human motivation can play an important role in drug abuse. 

He hopes the study results encourage psychiatrists and others to resist the temptation to assign drug abuse risk to either biological or psychological factors.

“In psychiatry, we go through periods of thinking everything is biological and then thinking everything is psychological,” Kendler said. “With drug abuse, brains are important and genes are important, but psychological factors are also significant. Human motivation can play an important role in drug abuse. This study has put that in pretty indisputable terms.”

Kendler, director of the Virginia Institute for Psychiatric and Behavioral Genetics at VCU, collaborated on the study with Dace Svikis, Ph.D., professor of psychology, psychiatry and obstetrics and gynecology at VCU, as well as with Lund University researchers Henrik Ohlsson, Ph.D.; Jan Sundquist, M.D., Ph.D.; and Kristina Sundquist, M.D., Ph.D.