A new study from the University of Colorado Boulder (CU) has found that marijuana use during pregnancy could increase the risk of sleep problems in children as much as 10 years later.

The study, published in Sleep Health: The Journal of The National Sleep Foundation, is the first one to suggest how prenatal marijuana use can affect sleep cycles in children.

Senior study author Dr. John Hewitt at CU said, “As a society, it took us a while to understand that smoking and drinking alcohol are not advisable during pregnancy, but it is now seen as common sense. Studies like this suggest that it is prudent to extend that common-sense advice to cannabis, even if use is now legal.”

Dr. Hewitt and lead author Evan Winiger looked at nearly 12,000 youth from age 9 or 10 into early adulthood. The participants’ mothers were asked whether they had used marijuana during pregnancy and if so, how frequently.

Nearly 700 mothers reported using cannabis during pregnancy, of which, 184 used it daily, while 262 used twice or more daily.

Winiger, who is a graduate student in the Department of Psychology and Neuroscience at CU, said, “Mothers who said they had used cannabis while pregnant were significantly more likely to report their children having clinical sleep problems.”

Among children whose mothers used marijuana frequently were more likely to report symptoms of excessive sleepiness, trouble waking in the morning, and fatigue throughout the day.

However, the researchers warned that the study has a few limitations.

Winiger said, “We are asking mothers to remember if they smoked marijuana 10 years ago and to admit to a behavior that is frowned upon,” suggesting that actual rates of prenatal use could be higher.

It is unclear exactly how marijuana exposure during vulnerable developmental times might shape future sleep patterns in children. However, animal studies have shown that tetrahydrocannabinol (THC) and cannabinoids adhere to CB1 receptors in the developing brain, affecting areas that regulate sleep.

Meanwhile, the researchers caution that pregnant women should be wary of using marijuana as an antidote to morning sickness. Dr. Hewitt concluded, “This study is one more example of why pregnant women are advised to avoid substance use, including cannabis. For their children, it could have long-term consequences.”