New research links marijuana use to excessive daytime sleepiness in adolescents.

Researchers from Nationwide Children's Hospital found that 10 percent of adolescents sent to a Sleep Center for evaluation of excessive daytime sleepiness with testing results consistent with narcolepsy had urine drug screens positive for marijuana, confounding the results.

"Our findings highlight and support the important step of obtaining a urine drug screen, in any patients older than 13 years of age, before accepting test findings consistent with narcolepsy, prior to physicians confirming this diagnosis," Mark L. Splaingard, senior author on the study, said in a statement. "Urine drug screening is also important in any population studies looking at the prevalence of narcolepsy in adolescents, especially with the recent trend in marijuana decriminalization and legalization."

For the 10-year study, researchers collected and analyzed data from nearly 400 children to examine the prevalence of positive drug screens in pediatric patients undergoing standardized multiple sleep latency test (MSLT.)

They found that 43 percent of children with urine drug screens positive for marijuana actually had test results consistent with narcolepsy or abnormal REM sleep patterns. No child younger than 13 years of age had a positive urine drug screen. The data showed that males were more likely to have a positive urine drug screen and MSLT findings consistent with narcolepsy.

"We believe that many of the children who had positive urine drug testing for marijuana and testing consistent with narcolepsy had improvement of the symptom of excessive day time sleepiness after enrollment in a community drug program, because most didn't come back for repeat diagnostic studies once they were drug-free," Splaingard said.

The findings are detailed in the Journal of Clinical Sleep Medicine.