Research Finds Prenatal THC Exposure Negatively Affects Brain Development

The cannabis industry is expected to reach $2.1 billion in sales by 2020, for both hemp-derived and marijuana-derived CBD, an increase of 700% compared to 2016 sales.

However, this rapidly growing market brings negative externalities to society. Dr. Geoffrey Vargish is one scientist who is trying to answer some of the questions about the safety of cannabis.

Dr. Vargish conducted a study for his dissertation work at the National Institute of Child Health and Human Development to determine if cannabis exposure before birth has any effect on a child’s development.

Initial studies were conducted on mice and compared to human brain development.

Geoff Vargish

Cannabinoid Differences

During our interview, Dr. Vargish explained that within the cannabis plant, we find two main cannabinoid compounds:

  • Cannabidiol (CBD): the main non-psychoactive component.
  • Tetrahydrocannabinol (THC): the main psychoactive component of the cannabis plant.


Vargish's Observations

He went on to tell us that our body produces its own cannabinoids as well. These are called endogenous cannabinoids, and evidence suggests that they are involved in various aspects of brain development.

Hemp-derived CBD products only contain trace quantities of THC (less than 0.3%).

Marijuana-derived CBD products often contain higher amounts of THC (5%-30%).

Since CBD is a non-psychoactive compound and THC is a psychoactive compound, the bulk of Dr. Vargish’s research focused on THC Suggests… While this study has negative implications, it does not necessarily mean that all cannabis derived products will have this effect.

As this study focused on exclusively on THC, it remains unclear whether a pure CBD derivative, like those found in hemp or a CBD isolate, will have a similar effect during pregnancy.

In addition, Dr. Vargish explained that several limitations need to be taken into account.

For example, this study was conducted in mice, making it difficult to predict whether the behavioral deficits Dr. Vargish observed will translate to humans. While previous studies on humans have found that neurobehavioral deficits are associated with prenatal cannabis exposure, more research is needed to fully understand the relationship between prenatal cannabis exposure and human brain development.

However, now that marijuana is recreationally legal in several states, and legal for medicinal purposes in even more, scientists are optimistic that large-scale, continuous studies tracking how cannabis exposure influences human development will be possible.

*”Limited Use” is hemp-derived CBD containing less than 0.3% THC

Dr. Vargish went on to clarify that there is not a lot of research on how exposure to different potencies of CBD and THC can affect the body’s development. He explained that the amount of THC that the mice were exposed to was fairly moderate, but through modern cross-breeding techniques, higher THC and CBD values can be obtained.

Traditionally, the amount of THC found in a cannabis plant would be around 8.5 percent. Today, it is not uncommon to find strains with THC levels around 40 percent.

Obstacles Obtaining Cannabinoids

Cannabis research was met with various obstacles because it is a Schedule I Narcotic.

“One of the big issues with anything that is Schedule 1 is [it is] going to be very difficult to get grant funding and do research unless it is going to prove negative consequences of that [substance].


And then second, if you do get grant funding, you have very limited access to the compounds you want to study… We had to work with the National Institute on Drug Abuse, which is in Baltimore. I know there was quite a bit of paperwork that my boss had to fill out. Then eventually we were allocated a small quantity which we had to track and log extensively,”

Since only a small amount of THC could be acquired, Dr. Vargish had to substitute WIN55.212-2, which is a synthetic cannabinoid with properties similar to THC, and do a parallel study in order to complete the research.

Further Research Necessary

As cannabis de-regulation continues, demand for the plant will continue to grow. It is essential that studies on the effects of THC and CBD on the human body continue in order to determine the full range of benefits and risks associated with these compounds, particularly as THC concentrates continue to grow in popularity.

While hemp-derived CBD does not have the same effects as those found in this THC study, it is just as important to fully understand the effects of CBD and all other cannabinoids on the human body.


Dr. Geoffrey Vargish is a postdoctoral fellow in Dr. Takao Hensch’s lab at Harvard University and Boston Children’s Hospital, where he studies how experience shapes brain development. Prior to joining the Hensch lab, Geoffrey obtained his undergraduate degree from the University of Miami and a Master’s in Public Health from Drexel University. He then went on to earn his PhD in neuroscience as part of the Brown University/National Institutes of Health graduate partnership program. He completed his dissertation work in the lab of Dr. Chris McBain at the National Institute of Child Health and Human Development (NICHD), examining how prenatal exposure to cannabinoids influences neuronal development. For further related reading on the topic please view the related links:

  1. Prenatal exposure to marijuana may disrupt fetal brain development, mouse study suggests
  2. Persistent inhibitory circuit defects and disrupted social behaviour following in utero exogenous cannabinoid exposure
  3. The Hyperpolarization-Activated Cation Current Ih: The Missing Link Connecting Cannabinoids to Cognition
  4. Identifying Prenatal Cannabis Exposure and Effects of Concurrent Tobacco Exposure on Neonatal Growth
  5. Pregnant Women Turn to Marijuana, Perhaps Harming Infants (NY Times)
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