BOULDER, Colorado — Prenatal marijuana use by pregnant mothers increases the chance of developing childhood sleep problems, according to a study from University of Colorado (CU) Boulder.

After studying nearly 12,000 children who were 9- and 10-years-old, researchers said they were more likely to experience problems including trouble falling asleep and waking in the night if their mother used marijuana.

Researchers also said that when pregnant mothers used marijuana more frequently, it increased the chance their children would experience excessive sleepiness during the day and have trouble waking up in the morning.

>The video above from February 2020 is about a study showing more teens are choosing to not use marijuana.

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Participants’ mothers were asked if they had ever used marijuana while pregnant and how frequently. They were also asked to fill out a 26-item survey on their child’s sleep patterns.

Researchers said questions included how easily they fell asleep, how long they slept, whether they snored and how sleepy they were during the day.

Around 700 mothers reported using marijuana while pregnant, 184 used it daily, and 262 used it twice or more daily, according to the study.

Researchers said a clear pattern emerged after controlling for factors including the mother’s education, parent marital status and family income and race.

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

While smoking cigarettes and drinking alcohol during pregnancy has declined in the U.S., researchers said marijuana use among pregnant women has increased by 7%.

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Winiger suggested that the study did have some limitations, and that actual rates of prenatal marijuana use may have been higher than the study found: 

“We are asking mothers to remember if they smoked marijuana 10 years ago and to admit to a behavior that is frowned upon,” Winiger said.

Researchers said the study doesn’t prove marijuana use while pregnant causes sleep problems, but said it does add on a small but growing body of evidence of a link between them.

Other studies on infant and three-year-old children found similar results, researchers said.

CU Boulder said the authors and colleagues have also found through studies that teenagers who frequently smoked marijuana were more likely to develop adult insomnia.

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Researchers are not sure how marijuana exposure during developmental times impacts sleep, but said animal studies suggest THC and other cannabinoids attach to CB1 receptors in the developing brain, influencing regions that regulate sleep.

“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,” said senior author John Hewitt, director of the Institute for Behavioral Genetics at CU Boulder. “Studies like this suggest that it is prudent to extend that common sense advice to cannabis, even if use is now legal.”

The authors said mothers-to-be should be wary of dispensaries that recommend marijuana use for morning sickness.

“This study is one more example of why pregnant women are advised to avoid substance use, including cannabis,” Hewitt said. “For their children, it could have long-term consequences.”

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