Mental Health Update | Young adults who started using cannabis regularly before age 18 were more likely to report later sleep troubles, according to a study published online in Sleep.
“People tend to think that cannabis helps with sleep, but if you look closely at the studies, continued or excessive use is also associated with a lot of sleep deficits,” said study lead author Evan Winiger, a graduate student in the Institute for Behavioral Genetics at the University of Colorado-Boulder. “Our study adds to that literature, showing for the first time that early use is associated with increased rates of insomnia later on.”
The study included 1882 twins, with an average age of 23 years, from the Colorado Twin Registry. Participants completed surveys about marijuana use, sleep habits, mental health, and other factors.
Approximately a third of participants who used cannabis regularly before age 18 experienced insomnia as adults, compared with less than 20% of participants who did not use cannabis regularly as teenagers, the study found. What’s more, 10% of participants who used cannabis regularly as teens had issues with “short sleep,” or sleeping fewer than 6 hours per night regularly. Just 5% of participants who did not report early cannabis use experienced short sleep.
Participants who began using marijuana after age 18 also had slightly increased rates of insomnia as young adults, according to the study. Rates remained elevated after researchers controlled for depression, anxiety, and shift work.
The study, which spanned 472 pairs of identical twins and 304 pairs of fraternal twins, also found that many genes that contributed to risk of early onset of regular cannabis use were also linked with insomnia and short sleep. 
“It is possible,” researchers wrote, “that sleep problems could influence cannabis use, cannabis use could influence sleep problems, or common genetics could be responsible.”
At any rate, young people should avoid using cannabis as a way to improve sleep, Winiger advised.
“We would not recommend that teenagers utilize marijuana to promote their sleep,” he said. “Anytime you are dealing with a developing brain, you need to be cautious.”
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