Cannabis on the mind: Study finds connection between sleep, memory and marijuana use

Miriam Fauzia, The Dallas Morning News

DALLAS — As public support for marijuana decriminalization grows, new research is shedding light on the drug’s impact on sleep and memory.

In a recent study published in The American Journal of Drug and Alcohol Abuse, researchers at the University of Texas at Dallas found that adults with cannabis use disorder tended to experience poorer sleep than those without the condition. They also performed more poorly on tests assessing visuospatial memory, or the ability to retain and process information about an object’s appearance and location.

“What this paper does is provide a bridge between the two things” — sleep and memory — “and helps establish that perhaps some of the memory impairment associated with cannabis use is indeed due to poor sleep quality,” said Christopher Verrico, an associate professor of psychiatry research at Baylor College of Medicine, who was not involved in the study.

The study also underscores the many unknowns surrounding marijuana’s impact on the human body and the need to be cautious when using it, said Ashley Garling, a clinical assistant professor at the University of Texas at Austin College of Pharmacy who was not involved in the study.

In a 2022 survey of more than 27,000 people between ages 16 and 65 in the U.S. and Canada, almost half reported using cannabis to help with sleep. In another survey, commissioned by the American Academy of Sleep Medicine in 2023, a quarter of Americans reported occasionally or regularly using pot to help them stay or fall asleep. And parents with children under 18 living at home were more likely than nonparents to use marijuana as a sleep aid — 30% versus 19%.

Whether marijuana actually helps you fall asleep isn’t clear. Some studies and surveys suggest it doesn’t improve sleep while others suggest it might, particularly in people with conditions that interfere with sleep like chronic pain.

Additionally, the two main active ingredients in marijuana — delta-9-tetrahydrocannabinol (THC), a psychoactive chemical that makes you feel high, and the non-psychoactive cannabidiol (CBD) — influence sleep in different ways. Low doses of THC may improve sleep while higher doses may disrupt it. The opposite is true for CBD.

Studies have shown that long-term marijuana use can impair cognitive function depending on what age someone starts using. A 2016 study tracking over 3,000 middle-aged adults over two decades found that for those who used pot for more than five years, their verbal memory was worse compared to those who used marijuana less often. A 2018 study found that young people who used marijuana frequently were more likely to score slightly lower on memory tests and not do as well at learning new information and higher-level problem solving compared to their non-using peers. A separate 2018 study found cognitive performance among young cannabis users improved when they stopped using.

But studying marijuana’s effect on both memory and sleep had not been done before, said Francesca Filbey, director of the University of Texas at Dallas’ Cognitive Neuroscience Laboratory of Addictive Disorders, who led the new study.

“Memory has been widely known to be a potential impairment as a result of cannabis use,” Filbey said. “But we don’t know yet what the mechanisms are. We especially don’t know how that relates to people who use cannabis as a sleep aid.”

To answer that, Filbey and Tracy Brown, the study’s first author and a PhD student at the University of Texas at Dallas, surveyed more than 200 people from Dallas and the Netherlands about their sleep quality within the past week. One hundred and forty-one respondents had cannabis use disorder, a condition marked by a dependency on marijuana that affects three in 10 people who use it; the other 87 had used marijuana in the past but not as frequently and not within the three months prior to the study.

Those with cannabis use disorder reported more sleep problems compared to the other group. They also tended to perform not as well on tests assessing their visuospatial memory.

While this finding indirectly ties marijuana use to memory, Brown said there is likely an underlying mechanism: the endocannabinoid system, a recently discovered signaling network that regulates sleep, learning and memory, among other functions. Cannabinoids, the chemicals at the heart of this system, are produced naturally by our bodies and are found in marijuana.

“What we know about the endocannabinoid system is that it’s a regulatory process within its own right, but it signals circadian rhythms, our sleep-wake cycles,” Brown said, with some hormones spiking in the morning and others lowering in the evening. He added that sleep is crucial for the brain’s ability to consolidate new information into memories.

The next step to exploring marijuana’s impact on sleep and memory will be to study brain activity during sleep to gauge how restorative it is in real time. Future studies will also need to investigate how differing amounts of THC and CBD in the body affect sleep and memory, said Garling of UT Austin, who added that the amounts vary based on how cannabis is taken.

Filbey and Brown emphasized this study is just the first step to a better understanding of how cannabis impacts the brain and that more studies are needed given the public health concern posed by its widespread acceptance.

“With any type of medication, you have all these different clinical trials. But [with] cannabis, it’s putting the cart before the horse,” Brown said. “We’re legalizing it, not necessarily at the federal level but the state level, for medicinal and recreational [use]. But the fact that it’s being legalized for medicinal use is informing people that this is something safe or effective. We don’t have that kind of research yet.”

Under federal law, marijuana is classified as a Schedule I drug, with a high risk of abuse and no legal use. Though exceptions can be made with permission from the Drug Enforcement Agency, this classification has posed a significant roadblock for clinical research, Filbey said. But she is optimistic that will soon change. In April, the DEA announced that it would consider bumping marijuana down to a Schedule III drug. It would remain a controlled substance, but the move would acknowledge its potential medical uses and make research easier.

Medicinal marijuana in Texas is legal only for people with conditions including severe epilepsy, autism, cancer and PTSD. Outside of those conditions, cannabis use and possession continues to be penalized.

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