Recreational users of the drug known as ecstasy may be at a higher risk for sleep apnea, according to a study published in the December 2 online issue of Neurology, the medical journal of the American Academy of Neurology. The study found that the risk of apnea was higher for ecstasy users than for those who were obese.

“People who use ecstasy need to know that this drug damages the brain and can cause immediate and dangerous problems such as sleep apnea,” said study author Una McCann, MD, of John Hopkins School of Medicine, Baltimore.

The researchers tested 71 people who had used ecstasy 25 times or more, and 62 people who had never used ecstasy. Ecstasy users had more than eight times the risk of sleep apnea compared to people who did not use the drug. The two groups had a similar rate of people with mild sleep apnea (21% of ecstasy users and 27% of nonusers), but only ecstasy users had moderate or severe apnea, with eight cases (13%) of moderate apnea and one case (about 1%) of severe apnea. The length of time a person had used ecstasy was correlated with a higher rate of sleep apnea episodes.

“Our findings may be explained by how ecstasy damages neurons related to serotonin, a chemical in the brain that is involved in sleep regulation and breathing, among other important functions,” said McCann. “Sleep apnea in itself is dangerous, but it can also contribute to thinking problems in people who use ecstasy because chronic sleep disruption is known to have a negative effect on how a person functions during the daytime.”

The study was supported by the National Institute on Drug Abuse.