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For some, the drowsiness and relaxation that comes from marijuana use can be helpful for sleep. However, research from the University of Colorado Boulder suggests that this potential sleep aid could instead be an impediment.

This is one of the implications of the research of Evan Winiger (PhDPsych’21), whose doctoral dissertation shows evidence connecting frequent cannabis use with a range of early and late sleep problems—which is the first direct evidence of cannabis use and sleep’s shared genetic relationship.

At the top of the page: Cannabis plant growing under LED grow lights. Photo by on . Above: Evan Winiger is a postdoctoral research fellow at University of Colorado Anschutz examining the relationships of cannabis and sleep.

“There’s a kind of big misconception in the role that cannabis can have as a sleep aid. We see some evidence that when you use it frequently and you use it early, it might be associated with long-lasting or some potential drastic effects on your sleep quality,” Winiger, now a postdoctoral research fellow at University of Colorado Anschutz, said.

When consuming marijuana, the plant’s tetrahydrocannabinol (THC)—or the substance that gets people high—and cannabidiol (CBD)—a chemical compound essential to many medical applications—are activated in the endocannabinoid system, an important bodily system for brain and nervous system function.

THC binds to CB1 and CB2 receptors, which are found in the nervous and immune systems, respectively. CB1 receptors, in particular, are thought to regulate sleep processes such as the sleep-wake cycle and seem to not be as successful with chronic cannabis use.

Furthermore, research has shown high-doses of CBD help sleep, but high-doses of THC seem to obstruct sleep.  

“Our brain does a lot when we sleep: It repairs, organizes and consolidates memories. In terms of how cannabis influences sleep, very acute limited use has shown to help sleep, but when we see heavy chronic use, daily use, it’s associated with a host of sleep deficits, including insomnia, lower sleep duration, sleep-quality issues and longer sleep onset latency. It is thought that chronic or heavy use is associated with the desensitization of the CB1 receptors and CB1 activity and efficacy, which facilitates waking,” Winiger said.

Twin modeling was used in this collection of work, which allows researchers to look at biological twins to examine the degree to which genetic and environmental factors influence a trait or disorder, and is an initial step in pinpointing the genetic relationships. 

Winiger and his team also utilized genomic methods to test many sleep traits and substance use traits to find significant genetic correlations.

Using a method called polygenic risk prediction, or a method to estimate an individual's lifetime genetic risk of disease, Winiger found that the genetics that potentially contribute to insomnia can also predict cannabis use traits such as age of first use and use behaviors.

Further application of genomic methods led Winiger to determine significant genetic correlations between lifetime cannabis use and evening chronotype (individual differences in sleep timing), as well as genetics links between cannabis use disorder and both short sleep duration and insomnia. 

“If genetic variation accounts for the association (of cannabis and sleep), that then leads us to look at how genetic variants, such as in the endocannabinoid system, might affect sleep patterns; (how) genetic variants for sleep or circadian rhythms might influence propensity to use cannabis; or, indeed, whether some other system related to genetic determinants of impulsive behavior, for example, might influence both cannabis and sleep,” said John Hewitt, director of the Institute of Behavioral Genetics and professor of psychology and neuroscience.

“Motivated by the twin study results, Evan went on to also utilize genomic data to confirm these genetic associations.”

Along with the twin and genomic studies, Winiger also examined how cannabis use during pregnancy might affect sleep in children. The results suggest that general exposure to cannabis during pregnancy may be associated with childhood sleep deficits, which can lead to sleep disorders.  

“The endocannabinoid system is very instrumental and operational in early pregnancy, and it holds a crucial role in both prenatal brain and embryonic development,” Winiger said. “The fetal brain is thought to be densely populated with CB1 receptors, and these escalate during gestation and are believed to actually impact brain development. So THC binds to these receptors and there's evidence that suggests it possibly alters neuro (brain) development.”

Winiger is continuing his research on cannabis and sleep with his current postdoc, looking at the further questions stemming from his dissertation.

“This body of work really is the first collected evidence of cannabis use having a genetic relationship with sleep deficit,” Winiger said.