Study to look at effects of alcohol and marijuana use during pregnancy

Dr. Brian Christie

Pictured: Dr. Brian Christie. Image source: University of Victoria.

As attitudes and regulations around cannabis use change around North America, a growing number of adults aged 19 to 30 years report using cannabis; a not-insignificant proportion of these report simultaneous use of alcohol and marijuana (SAM). For young women, this can present an increased risk of unplanned pregnancy, but can also mean engaging in potentially risky behaviours in the early stages of gestation before an individual knows they are pregnant.

A new study funded by a Catalyst Grant from the Canadian Institutes of Health Research (CIHR) will look at the effects of SAM on fetal brain development in rats, filling a gap in our understanding of sex-specific experiences with cannabis and alcohol, and how SAM may alter function and growth in key areas of the brain.

“As a public health issue, SAM is still not well recognized or understood,” explains Dr. Brian Christie, a principal investigator with the Djavad Mowafaghian Centre for Brain Health and Professor in the Island Medical Program and Division of Medical Sciences at the University of Victoria. “We know the effects of prenatal ethanol exposure, but cannabis is more widely available now and given the variability in products available, it can be harder to know how much individuals are consuming, to measure both the dose and the potency, and to assess the health implications of specific cannabinoids.”

The study, Double Jeopardy: Effects of Prenatal Cannabis and Ethanol Exposure on hippocampus structure and function, will build on Dr. Christie’s extensive research using models Fetal Alcohol Spectrum Disorder (FASD) as well as his team’s experience in examining the role of cannabinoids in synaptic plasticity. 

Cannabinoids are compounds in cannabis that act on specific neurotransmitter receptors in the brain. Commonly known cannabinoids include tetrahydrocannabinol (THC), cannabidiol (CBD) and cannabinol (CBN); these exist in different cannabis varieties in varying amounts. In October 2018, the Society of Obstetricians and Gynaecologists of Canada warned that THC, a psychoactive component of cannabis, can cross the placenta and potentially cause harm to the developing fetus.

In adults, cannabis can affect synaptic function and reduce the number of synapses in the brain. Prenatal exposure to cannabinoids can alter the trajectory of early brain development, but little research exists on how SAM use during pregnancy impacts the structure and function of the hippocampus, a brain region known to be involved in learning, memory, and emotional processes.

“We’re looking at this as an addiction issue,” explains Dr. Christie. “While cannabis proponents argue that cannabis itself is less addictive, we know that alcohol is an addictive substance. We’re hoping to uncover how prenatal exposure to cannabis and alcohol works at the developmental level.”

A study published by researchers at the University of British Columbia in January 2019 found that up to one third of pregnant women do not believe cannabis is harmful to their fetus; pregnant cannabis users were more likely to be under 25 years of age. According to Dr. Christie, individuals are almost twice as likely to use cannabis and alcohol simultaneously.

“We used to work to make people aware of the risks of alcohol and tobacco for a developing fetus,” explained Dr. Christie. “This generation’s issue is not dissimilar; we’re hoping that this research will provide clarity around the risks of mixed substance use, and improve public health outcomes.”