Children born to mothers who use cannabis during pregnancy are more likely to have an abnormal brain structure, which may have long-term consequences for mental health.
This is the conclusion of a new study published in the journal Biological Psychiatry, led by Dr. Hanan El Marroun, of Erasmus University Medical Center in the Netherlands.
According to the researchers, around 2-13 percent of women worldwide use cannabis during pregnancy.
Previous research has suggested that expectant mothers who use the drug are more likely to have children with behavioral and mental health problems.
Exactly how cannabis use affects the brain structure of offspring, however, has been unclear, and this is what Dr. El Marroun and colleagues set out to investigate.
“This study is important because cannabis use during pregnancy is relatively common and we know very little about the potential consequences of cannabis exposure during pregnancy and brain development later in life,” says Dr. El Marroun.
“Understanding what happens in the brain may give us insights in how children develop after being exposed to cannabis.”
The team analyzed the data of 263 children aged 6-8 years who were part of the Generation R Study – a population-based study in the Netherlands, in which they were followed from birth.
Of these children, 96 were born to mothers who used cannabis during pregnancy, and most of these mothers were also smokers. A total of 54 children were prenatally exposed to tobacco only, while 113 were not prenatally exposed to either substance.
All of the children underwent magnetic resonance imaging (MRI) scans, which allowed the researchers to assess their brain volume and cortical thickness.
Overall, the researchers found no difference in total brain volume, gray matter volume, or white matter volume between the three groups.
However, compared with children who were prenatally exposed to tobacco only, the researchers found those who were prenatally exposed to both cannabis and tobacco had a thicker prefrontal cortex.
The prefrontal cortex is a brain region that plays a role in complex cognitive behavior, planning, decision-making, working memory, and social behavior.
Given the increase in legalization of cannabis across the United States, Dr. John Krystal, editor of Biological Psychiatry, believes expectant mothers should take note of these findings.
“The growing legalization, decriminalization, and medical prescription of cannabis increases the potential risk of prenatal exposure. This important study suggests that prenatal exposure to cannabis could have important effects on brain development.”
Dr. John Krystal
Additionally, the researchers found that children who were prenatally exposed to tobacco only had a thinner prefrontal cortex than those who were not prenatally exposed to tobacco or cannabis.
Dr. El Marroun says the study results should be interpreted with caution, noting that further studies are needed to determine the underlying mechanisms that link prenatal cannabis exposure to changes in brain structure.
“Nevertheless,” she adds, “the current study combined with existing literature does support the importance of preventing smoking cannabis and cigarettes during pregnancy.”