Researchers found children whose moms used marijuana while pregnant suffered from somnolence symptoms — or excessive sleepiness.

Using cannabis while pregnant could cause your child sleeping problems later in life, according to a new study by University of Colorado Boulder researchers. The research doesn’t establish a causality between prenatal marijuana exposure and developmental sleep problems, but it does represent another possible development issue caused by pregnant women consuming marijuana.

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

The study, published in Sleep Health: The Journal of The National Sleep Foundation, analyzed data compiled for the landmark Adolescent Brain Cognitive Development (ABCD) study, which has followed 11,750 children since they were 9 or 10 years old. The ABCD study launched in 2015 and will become the largest long-term study to explore early brain development in the United States.

Participants’ mothers were given an exhaustive questionnaire upon entrance into the ABCD study. One query was whether moms had consumed cannabis while pregnant. And if so, how much did they use? They weren’t asked about consumption method, meaning we don’t know if they smoked cannabis, ate edibles, or used tinctures. About 700 of the moms admitted to using marijuana while pregnant — 184 used daily, 262 did so twice or more per day.

“Mothers who said they had used cannabis while pregnant were significantly more likely to report their children having clinical sleep problems,” said the study’s lead author Evan Winiger.

There are obvious limitation to this study, which researchers readily admitted. Marijuana use remains federally illegal and researchers wondered if actual prenatal cannabis use had been higher among the ABCD dataset.

“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.

The research team also linked teen marijuana use to adult insomnia in a study earlier this year. Scientists, however, still don’t completely understand how marijuana use while pregnant affects childhood development. A comprehensive review of previous research worried that scientists have oversimplified the link between prenatal cannabis exposure and childhood cognitive development.

“The current review of the literature found that there are relatively few cognitive alterations noted in offspring exposed to cannabis prenatally,” the review’s authors wrote.