Young people with chronic or severe depression are at elevated risk for developing a problem with cannabis in later adolescence, according to a new study from the University of Washington.

The study, led by Isaac Rhew, adjunct research assistant professor at the UW School of Public Health, interviewed 521 students from four Seattle public middle schools. Researchers used data from annual assessments of the students at ages 12 to 15 and then again at 18.

“The findings suggest that, if we can prevent or reduce chronic depression during early adolescence, we may reduce the prevalence of cannabis-use disorder,” said Rhew, a graduate of the Department of Epidemiology who works primarily as a research assistant professor of psychiatry and behavioral studies at the UW School of Medicine. The results were published online July 17 in the journal Addiction.

What researchers called “a 1 standard deviation increase” in cumulative depression during early adolescence was associated with a 50 percent higher likelihood of cannabis-use disorder in the study.

The researchers were surprised by data indicating that the prevalence of cannabis- and alcohol-use disorder in this study was notably higher than national estimates, with 21 percent meeting criteria for cannabis-use disorder and 20 percent meeting criteria for alcohol-use disorder at age 18.

What effect the easing of marijuana laws in Washington state had on the youth is unclear. Researchers said it would be informative to conduct a similar study in a state with stricter marijuana laws to understand whether the relationship between depression and later cannabis misuse is similar.

Study authors include UW researchers Charles Fleming, Ann Vander Stoep, Elizabeth McCauley and Semret Nicodimos. Co-author Cheng Zheng is with the Zilber School of Public Health at the University of Wisconsin-Milwaukee.