Using marijuana in college may increase the risk of leaving school, a new study suggests. Researchers found even students who only used marijuana occasionally were more likely to leave than their peers who did not use drugs.

The study included 1,133 college students, who were followed over four years. The researchers found students who used marijuana more than 17 days a month were twice as likely as those who used marijuana less than a day per month to have an enrollment gap while in college, HealthDay reports. Even students who used marijuana three to 12 days a month were more likely to have an enrollment gap, compared with those who did not use marijuana.

Drugs other than marijuana also were significantly associated with leaving college, the study found.

Continuous enrollment was defined as being enrolled in college for at least one credit during each fall and spring semester for the first four years, the article notes.

“We wanted to look at whether or not drug use interferes with goals students had set for themselves. Our results show that marijuana use is not a benign thing,” said lead researcher Dr. Amelia Arria, Director of the Center on Young Adult Health and Development at the University of Maryland School of Public Health. The findings appear in the Journal of Studies on Alcohol and Drugs.

In a second study, published in the journal Psychiatric Services, Dr. Arria found students who experience depression symptoms and seek treatment in college may be at risk for an enrollment gap, particularly if they use marijuana or other illegal drugs.

If students’ depression was identified and treated before they went to college, they were not at risk for enrollment gaps, the study found.