Children’s brains may be affected by marijuana use during pregnancy

June 21, 2016 Providence Health Team

Marijuana use during pregnancy appears to be associated with abnormal brain structure in children, but researchers say they aren’t sure what this could mean for a child’s development.

In a study published in Biological Psychiatry, a team made up mostly of Dutch researchers says it found an association between prenatal marijuana use and the thickness of the child’s prefrontal cortex, which is used for decision making.

"Understanding what happens in the brain may give us insights in how children develop after being exposed to cannabis," said the principal author, Hanan El Marroun of Erasmas University Medical Center in the Netherlands. Cannabis is the plant that produces marijuana as well as other drugs containing THC, such as hash oil.

What researchers found

Previous studies have examined how prenatal marijuana use affects children’s behavior, but little is  known about how such use affects the biology of the brain.

Researchers selected a group of 54 children ages 6 to 8 whose mothers used marijuana during their pregnancy. A study of brain scans found that these children had a thicker prefrontal cortex than children whose mothers didn’t use the drug during pregnancy.

The researchers indicated that not enough work has been done in this area to know what this could mean for the children.

"This study is important because cannabis use during pregnancy is relatively common,” said El Marroun, “and we know very little about the potential consequences of cannabis exposure during pregnancy and brain development later in life."

"We have to be careful interpreting the results of the current study," said El Marroun, who called for further research. "Nevertheless, the current study combined with existing literature does support the importance of preventing smoking cannabis and cigarettes during pregnancy."

What the prefrontal cortex does

The Dutch researchers say from 2 percent to 13 percent of women worldwide use some form of cannabis while they’re pregnant.

The prefrontal cortex is the center of what are known as the brain’s executive functions. These include:

  • Judgment
  • Problem solving
  • Decision making

The prefrontal cortex also is used short- and long-term memory, and helps control other areas of the brain during stressful events.

The Dutch study is available at the Biological Psychiatry website.

Growing use of marijuana

Marijuana use is legal in the Netherlands and increasingly in the United States, following adoption of new laws in Oregon, Washington and elsewhere. Many states also have legalized marijuana for medical use, including increasing appetite and reducing nausea.

The U.S. Justice Department continues to regard marijuana as a controlled substance and forbids its sale and distribution, but it says it’s working to make federal law consistent with state laws.

If you have concerns or questions about pregnancy, including marijuana use, talk to your health care provider. If you don’t have one, you can find a Providence provider here.

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