Over the course of the last decade, the use of cannabis in women of reproductive age has increased significantly as more states have legalized the recreational and medical use of cannabis. Despite decreasing rates of alcohol and tobacco use during pregnancy, cannabis use during pregnancy is on the rise. Many studies have raised concerns regarding the impact of prenatal cannabis exposure on child development and behavior. The most consistent findings are deficits in executive function and conduct problems observed in early or middle childhood. A recent study from researchers at Ohio State University assesses executive function and aggressive behavior in a preschool-aged cohort of children with prenatal exposure to cannabis.
As part of the Lifestyle and Early Achievement in Families (LEAF) cohort, pregnant individuals between the ages of 16 and 50 years were enrolled in a pregnancy research registry, and participants (n?=?355) who gave consent for future contact were invited to participate in a follow-up study evaluating children at 5 years of age. Cannabis exposure was assessed during pregnancy using urine toxicology, maternal self-report, and obstetric records. Executive function in children was evaluated by raters blinded to the child’s exposure status.
The analysis included 250 children of which 80 were exposed to cannabis (32%). Use of tobacco, other drugs, and/or alcohol during pregnancy was also common (39%, 26% and 22%, respectively). Most families were living in poverty. In this cohort, 155 children were Black/African American, non-Hispanic (62%); 11 were Hispanic (4%); 34 were multiracial or another race (14%); and 50 were White, non-Hispanic (20%).
Deficits in Executive Function and Aggressive Behavior Observed in Exposed Kids
Compared to unexposed controls, children with prenatal exposure to cannabis performed worse in two facets of executive function: inhibitory control and attention (0.4 SD) and planning (0.3 SD) after adjusting for potential confounders. There were no observed differences on assessments of measures of other executive functions, including cognitive flexibility and emotion regulation.
In addition, the researchers observed more aggressive behaviors in cannabis-exposed children. This finding is consistent with a previous study from the same group that observed increased aggressive behavior in 3.5-year-old children with prenatal exposure to cannabis.
What are the Long-Term Effects of Exposure?
Executive functions are a collection of cognitive processes, including inhibitory control, attention, working memory, and planning, that are responsible for goal-directed, problem-solving behaviors.
During the preschool years, executive functions undergo rapid development and differentiation, and this developmental milestone is predictive of academic and professional success. Deficits in executive function, specifically impulse control, may also confer vulnerability to substance use in adulthood.
The researchers hypothesize that cannabis interacts with endocannabinoid receptors, including CB1, which are highly expressed in the frontal lobe of the fetal brain, the region responsible for executive function, more specifically inhibitory control and attention.
Directions for Future Research
In this cohort study of 250 children, prenatal cannabis exposure was associated with worse attention, inhibitory control and planning ability on select laboratory-based assessments and with more aggressive behaviors. Results from this cohort where prenatal cannabis exposure was common and indicated that exposed children exhibited some differences in aspects of executive function and behavior that are relevant to long-term academic success and adaptive functioning.
The current study has many strengths, including the prospective assessment of cannabis use, standardized assessments of child outcomes conducted by raters blinded to cannabis exposure, and the consideration of multiple confounding variables. However, there are many limitations, and these are limitations that are intrinsic to all studies examining the effects of cannabis use during pregnancy.
In an accompanying editorial, Ran Barzilay, MD, PhD and Lauren K. White, PhD discuss many of the challenges involved in studying the effects of prenatal cannabis exposure on children’s neurocognitive development and behavior. In an observational study, it is essential to consider the significant differences between the exposed and unexposed groups. In this study, the differences between the two groups were observed in measures of socioeconomic status, use of other substances, maternal stress and mental health during pregnancy. While the authors were able to statistically adjust for these potential confounders, in a study of this size it is not possible to fully control for the effects of these other exposures.
Adverse exposures often co-occur and co-exist within a network of many other environmental and lifestyle factors, what is referred to as the exposome. In addition, neurodevelopmental outcomes are largely dependent on the caregiver, extending from in utero exposures to the postpartum environment and parenting through infancy and early childhood.
In order to disentangle the specific effects of prenatal cannabis exposure on neurodevelopmental outcomes from other relevant exposures, we need more large-scale studies that include diverse populations, incorporate multiple environmental confounders and rely on analytic methods tailored to take into consideration the causal effects of multiple exposures in observational studies.
While we cannot completely separate the effects of cannabis from other prenatal exposures, there is enough of a signal to raise concerns. We will continue to counsel women to avoid the use of cannabis during pregnancy. This requires careful screening in the obstetric setting, evaluation for other psychiatric disorders that may contribute to cannabis use, and resources to support abstinence in women with histories of cannabis use disorder.
Ruta Nonacs, MD PhD
References
Keim SA, Fried P, Yeates KO, Boone KM, Vrantsidis DM, Dean A, Murnan AW, Rausch J, Klebanoff MA. Prenatal Cannabis Exposure and Executive Function and Aggressive Behavior at Age 5 Years. JAMA Pediatr. 2024 Oct 28.
Barzilay R, White LK. Prenatal Cannabis Exposure-An Intergenerational Risk Marker for Neurodevelopment. JAMA Pediatr. 2024 Oct 28.
