Here is another reason to not use marijuana while pregnant. Exposure to cannabinoids, the chemical compounds of cannabis, was found to cause behavioral changes in male rats, making them antisocial. This effect, however, was not seen in female rats.

The study titled "Sex-dependent effects of in utero cannabinoid exposure on cortical function" was published on Sept. 11.

According to the Centers for Disease Control and Prevention, around 1 in 25 women in the United States report using marijuana while pregnant. While research is still looking into how this affects the fetus, most medical experts strongly discourage this practice.

Among various risks, past findings have suggested the possibility of low birth weight for newborns. There is also an increased likelihood for the baby to experience developmental problems

"As cannabinoids can cross the placenta, they may interfere with fetal endocannabinoid signaling during neurodevelopment, which is involved in regulating a variety of processes such as pregnancy, appetite, pain sensation, and mediating the pharmacological effects of cannabis," said senior author Olivier Manzoni, Inserm research director at the Mediterranean Institute of Neurobiology, and director of the CannaLab at the institute.

The long-term consequences of prenatal cannabinoid exposure are not clear, he said, also highlighting concerns that cannabis consumption during pregnancy is on the rise. In a 2017 study, for example, it was found that marijuana use among pregnant mothers in California increased from 4.2 percent to 7.1 percent between 2009 and 2016.

In the new study, researchers examined male and female rats, focusing on a specific region of the brain often implicated in neuropsychiatric disorders. They found that male rats exposed to cannabinoids while in the uterus were less sociable. Compared to regular animals, these rats spent less time interacting with others and also displayed abnormalities in their sniffing and playing behaviors.  

The observed changes were not limited to their external behavior. The researchers also found physical changes when examining the aforementioned brain region, noting an increase in the excitability of pyramidal neurons. However, none of these effects were seen in the female rats who were exposed to the drug while in the uterus.

"But while social interaction was specifically impaired in males, locomotion, anxiety, and cognition remained unaffected in both sexes, suggesting discrete and sex-specific behavioral consequences of cannabinoid exposure during adulthood," said co-first author Anissa Bara, who was a Ph.D. candidate in Manzoni's lab during the time the study was conducted.

These findings could support and strengthen doctors' advice for pregnant women to avoid using marijuana. Additionally, they also revealed a potential treatment strategy after noticing that the mGlu5 gene was reduced in the brains of exposed male rats.

In a test conducted later, the researchers were successfully able to reverse the effects of the cannabinoids by amplifying mGlu5 signaling and enhancing levels of anandamide in the rats. They hoped to see this being implemented in the future when creating pharmacological strategies for human trials.