Age of onset of regular cannabis use is predictive of lower adult sleep duration, according to a new study published in the journal Drug and Alcohol Dependence. The findings suggest that trouble sleeping is one of the developmental consequences for early cannabis use.

Evan A Winiger, the corresponding author of the new study, decided to investigate the topic after realizing that “the body of research focused on cannabis and sleep outcomes not only lacked prior twin studies, but also seemed to suffer from conflicting results in terms of if there is a beneficial or negative relationship between cannabis and sleep outcomes.”

“Additionally, there were only a couple of studies that showed early cannabis use was associated with later sleep factors and I wanted to investigate this possibility further,” said Winiger, a predoctoral trainee at the University of Colorado’s Institute for Behavioral Genetics.

The researchers examined data from 1,656 adult twins who were recruited from the Longitudinal Twin Sample and Colorado Twin Study. The participants reported how old they were when they first began using cannabis on a regular basis (at least once per month) and how many hours of sleep they typically get on weekends and on weekdays.

Most of the participants — 1,142 of them — reported never using cannabis regularly, while 282 participants reported using cannabis regularly after age 17 and 232 reported using cannabis regularly before age 17.

The researchers found that those who started using cannabis at a younger age tended to also report shorter sleep duration in adulthood.

“This paper shows that using cannabis regularly at a young age might have potential long-term effects on sleep outcomes, such that an earlier age of onset for regular cannabis use might be predictive and potentially causal for shorter sleep duration in adulthood,” Winiger told PsyPost.

“Additionally, we provide some preliminary evidence of a potential genetic correlation between onset of regular cannabis use and adult sleep duration, implying that the genetics responsible for early cannabis use could also be responsible for shorter sleep duration as an adult.”

The researchers controlled for factors such as sex, depression, and current tobacco/alcohol/cannabis use. But the study — like all research — includes some limitations.

“One of the major caveats of the study would be that, like other epidemiological studies, it doesn’t allow us to make definitive causal claims. Future studies need to use objective sleep measures such as actigraphy or accelerometers as they provide better measures of sleep duration and activity. Furthermore, future studies should look at the amount, frequency, and exact concentration (THC vs CBD) of cannabis used,” Winiger explained.

“I think as cannabis becomes federally legal and more studies are conducted, we will see more evidence of early, frequent, and continuous cannabis use being associated with maladaptive sleep outcomes.”

The study, “Onset of regular cannabis use and adult sleep duration: Genetic variation and the implications of a predictive relationship“, was authored by Evan A. Winiger, Spencer B. Huggett, Alexander S. Hatoum, Michael C. Stallings, and John K. Hewitt.