Regular cannabis use during adolescence may be linked to long-term insomnia risk. Digest
Adolescence is a critical window for brain development, and choices made during this time can shape long-term health. A twin study examined whether beginning regular cannabis use during the teenage years is connected to sleep problems in young adulthood.
Researchers examined 1,882 twins with an average age of 23, and grouped them by cannabis use history: early regular users who started at 17 or younger, later regular users who started after 17, and never-regular users. Sleep outcomes included clinically defined insomnia and a more severe pattern combining insomnia with short weekday sleep (under six hours). By comparing identical twins, who share nearly all their genes, with fraternal twins, who share about half, the team could estimate how much of the link between cannabis use and sleep was due to genetic influences.
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Key findings from the study:
- About 29 percent of early users reported insomnia, compared with 21 percent of later users and 19 percent of never-users. For the more severe type of insomnia, the rates were 9.9 percent in early users, 7.9 percent in later users, and 5.5 percent in never-users.
- Early regular users were more likely to report both forms of insomnia, even after taking mental health and other factors into account.
- Both the age at cannabis use onset and insomnia outcomes were strongly shaped by inherited factors. The same genetic influences contributed to both traits, indicating shared genetic liability rather than environmental overlap.
Several pathways could link early cannabis use with later insomnia. One involves circadian and genetic factors, as cannabis may interact with the biological clock systems and genes that regulate circadian timing. Another concerns neurodevelopmental effects: during adolescence, brain regions involved in regulating arousal and sleep-wake patterns are still maturing, and exposure to cannabis may interfere with their normal neurodevelopment. Lastly, cannabis acts directly on the endocannabinoid system, which plays a role in both sleep and circadian regulation.
Conclusion:
The results suggest that starting cannabis use before age 18 is linked to a higher likelihood of insomnia in young adulthood. There was substantial genetic influence on cannabis use, sleep problems, and their association. Because adolescence is a sensitive period, early cannabis exposure could heighten long-term insomnia risk by disrupting ongoing brain and biological development. Since the study relied on self-reports, retrospective cannabis histories, and lacked information on other substances at the time sleep was measured, more prospective research is needed to clarify the long-term effects. Learn more about how cannabis, alcohol, and other factors affect sleep in this clip featuring Dr. Matthew Walker.