A new study in Biological Psychiatry suggests that cannabis use during pregnancy is associated with abnormal brain structure.

The study compared children who were unexposed to cannabis in the womb and found that those that did had a thicker prefrontal cortex, the area of the brain that is associated with memory, decision-making and complex thought.

Study author Dr. Hanan El Marroun said with an estimated 2–13 per cent of women across the world using cannabis during pregnancy, the medical community still knows very little about the consequences of exposure and brain development later in life.

“Understanding what happens in the brain may give us insights in how children develop after being exposed to cannabis,” said El Marroun.

In the study, children who had been prenatally exposed to cannabis had magnetic resonance imaging of their brains and then compared those images to children who had been exposed to tobacco in the womb, along with children who had been exposed to neither substance.

The results found that tobacco and cannabis exposed children had differences in their cortical thickness.

“The growing legalization, decriminalization, and medical prescription of cannabis increases the potential risk of prenatal exposure,” said Biological Psychiatry editor Dr. John Krystal. “This important study suggests that prenatal exposure to cannabis could have important effects on brain development.”

El Marroun said more research needs to be done to determine the relationship between cannabis exposure and brain structure.

“Nevertheless, the current study combined with existing literature does support the importance of preventing smoking cannabis and cigarettes during pregnancy,” El Marroun said.