Smoking cannabis before the age of 15 could lead to insomnia later in life, a new study has found.
Researchers in the US discovered any history of using the drug was associated with an increased risk of reporting difficulty getting enough sleep.
Participants in the study reported struggling to fall asleep, difficulty maintaining sleep, experiencing non-restorative sleep and feeling sleepy during the day.
Scientists at the University of Pennsylvania in Philadelphia found the strongest association in adults who used cannabis before the age of 15.
"Current and past marijuana users are more likely to experience sleep problems," said lead author Jilesh Chheda, research assistant at the University of Pennsylvania in Philadelphia, working with Dr. Michael Grandner, the senior author on the study.
"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 was published recently in the online supplement of the journal Sleep.
To gather their results, researchers assessed a group of adults, ranging in age from 20 to 59, who responded to the 2007-08 National Health and Nutrition Examination Survey.
A history of drug use was reported by 1,811 participants.
Cannabis use was assessed as any history of use, the age a person first tried marijuana and the number of times a person used the drug in the last month.
Sleep-related problems were considered severe if they happened at least 15 days each month.
The results suggest that those who start using cannabis in adolescence may put themselves at higher risk of suffering insomnia later in life.
Researchers also concluded those who begin using the drug earlier could be more likely to experience trouble sleeping for other reasons, including stress.
The authors of the study said insomnia may be one of the reasons people start, or continue, to use marijuana.
But they go on to suggest the drug's use in combating sleep problems are likely to be ineffective, if they are still experiencing insomnia.
"Marijuana use is common, with about half of adults having reported using it at some point in their life," said Chheda.
"As it becomes legal in many states (in the US), 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."
According to the National Institute on Drug Abuse, marijuana use among young people has been increasing since 2007.
Some experts have linked the rise with increased public debate over the drug's legal status.
The federal government considers marijuana a Schedule I substance that has no medicinal uses and a high risk for abuse.
However, Colorado and Washington have legalised marijuana for adult recreational use, and 21 states have passed laws allowing its use as a treatment for certain medical conditions.
- Daily Mail