A new study suggests that marijuana can cause sleep impairment.

The research suggests marijuana users have a higher likelihood of reporting "difficulty falling asleep, struggling to maintain sleep, experiencing non-restorative sleep, and feeling daytime sleepiness," an American Academy of Sleep Medicine news release reported.

This phenomenon was twice as high in adult marijuana users who had started smoking before the age of 15.

"Current and past marijuana users are more likely to experience sleep problems," lead author Jilesh Chheda, research assistant at the University of Pennsylvania in Philadelphia, said in the news release. "The most surprising finding was that there was a strong relationship with age of first use, no matter how often people were currently using marijuana. People who started using early were more likely to have sleep problems as an adult."

The study subjects ranged in age from 20 to 59 years old, 1,811 of the participants had a history of drug use. The researchers looked at the participants' history of marijuana use, age of first use, and number of times used in the past month.

The researchers could not determine causality from this study, but the study suggests marijuana use is linked to insomnia-like symptoms. It also suggests that those who smoke marijuana earlier in life are more likely to experience stress-related insomnia.

Insomnia could also be the reason people continue to use marijuana .

"Marijuana use is common, with about half of adults having reported using it at some point in their life," Chheda said. "As it becomes legal in many states, it will be important to understand the impact of marijuana use on public health, as its impact on sleep in the 'real world' is not well known."

Marijuana use in young people has been on the incline since the year 2007, which could be associated with current debates on the drug's legal status.