Boston: Heavy marijuana use may increase the risk of insomnia, according to a new study which counters the popular belief that daily use of weed helps them sleep better.
Researchers at Boston University in the US found that daily marijuana users actually scored higher on the Insomnia Severity Index and on sleep-disturbance measures than those who did not use it daily.
The study's 98 subjects, mostly in their early 20s, were broken into three groups - daily marijuana users (49 people); those who were not daily users (29), defined as those who smoked at least one day in the past month and up to five days a week; and control group who did not use drug at all (20).
"Better sleep is one of the positive effects that marijuana users swear by, but there has been relatively little research on this topic," said Michael Stein, from Boston University.
Researchers cite previous research indicating that as many as one-third of young adults, ages 18 to 25, complain of sleep problems.
The study findings show that while occasional marijuana use does not disrupt sleep, heavy (or daily) marijuana use is associated with sleep difficulties.
"The effects of marijuana on sleep in intermittent users may be similar, in part, to those of alcohol, where improvements in sleep continuity measures have been reported with intermittent use. But "daily use results in the worsening of sleep," the researchers said.
The study examined sleep patterns in the three groups of young adults. The researchers found no significant differences in the sleep characteristics of those who did not use marijuana daily compared to those who did not use it at all.
Daytime sleepiness also did not differ among heavy users, lighter users, and nonusers.
"Sleep disturbance, which is common in this age group, may not be increased by non-daily use," researchers said.
While 20 per cent of the nonsmokers met the criteria for clinical insomnia, for the daily users meeting those criteria, it was 39 per cent.
Similarly, sleep disruption measures were worse for daily users than for occasional users.
"Study participants who did not smoke every day usually smoked in the evening, but once you are smoking multiple times a day, there is a greater chance that you will report disturbed sleep," Stein said.
"Only by stopping marijuana completely, and waiting some time without using at all, will a person be able to determine how marijuana was affecting, or not affecting, his or her sleep," added Stein.
In terms of gender (45 men and 53 women participated in the study), the research team found that women reported more sleep disturbance problems than men on several measures.
That finding was expected, Stein said, as insomnia is more common in women than men. Also, marijuana use has been shown to affect women's performance on neurological tasks more than it affects men's.
The study was published in the Journal of Addictive Diseases....