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Pregnancy research points to the role of will in substance use

August 3, 2017
by Gary A. Enos, Editor
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A population-based analysis examining women in Sweden found that risk of illegal drug abuse diminished significantly during pregnancy. While noteworthy in itself, it is what this finding suggests more broadly that has the study's researchers, and the agency that funded the study, energized.

In an interview with Addiction Professional, Virginia Commonwealth University (VCU) School of Medicine Professor Kenneth S. Kendler, MD, suggested that the study offers strong evidence of human volition's important role in the cessation of drug use. That carries substantial importance at a time when neurobiological explanations for, and solutions to, addiction have threatened for some to push aside the role of individual will.

“The value of this finding here is more theoretical,” Kendler explains. “It is showing how powerful this effect can be.”

Published online in June in the American Journal of Psychiatry, the National Institute on Drug Abuse-supported study used several methods to conduct a thorough analysis of women born in Sweden between 1980 and 1990 who gave birth between the ages of 20 and 35 (a group numbering nearly 150,000). Around 3,800 of these women had a drug abuse history. The team of researchers from the U.S. (VCU) and Sweden (Lund University) found that when compared with the equivalent time period immediately before pregnancy, drug abuse rates fell 78% during pregnancy.

In an effort to identify a possible causal relationship between pregnancy and decreased substance use, the researchers dug deeper, Kendler explains:

  • They controlled for women's socioeconomic status, a predictor of substance use problems, and found that the link between pregnancy and reduced use remained significant.

  • They examined pairs of identical twins in the study population, and found that there was an 83% reduced risk of drug abuse in a pregnant twin compared with her non-pregnant sister.

  • They conducted within-individual analysis over time and found that women's use during pregnancy was substantially lower than their use at times when they were not pregnant.

“I would challenge you to find more convincing evidence that causal stuff is going on,” says Kendler.

He adds, “Women use less frequently when pregnant [because] they are motivated to protect the health of the child.” Asked whether other factors during the time they are carrying a child might also contribute, Kendler says that the fear of losing custody of a child because of drug use needs to be considered, but he adds that this outcome rarely plays out in Swedish society.

Other findings

The motivation to protect the welfare of the child also might play into the study's finding that reduced use generally persisted for up to two years after a woman gave birth.

In addition, the study found that a husband's drug use decreased during the time when his wife was pregnant, though not to the same degree as the mother-to-be's use.

Kendler, a professor of psychiatry and human and molecular genetics at the medical school, adds that a spouse's continued substance use was identified as a factor that can counteract the protective effect of pregnancy on a woman's use.

Clearly, pregnancy never could be prescribed as a remedy for problematic substance use. These potent findings, however, say to Kendler that human will still plays an important role in patterns of substance use.

“With drug abuse, brains are important and genes are important, but psychological factors are also significant,” Kendler said in a news release from the university. “Human motivation can play an important role in drug abuse. This study has put that in pretty indisputable terms.”