Many patients over age 50 who use marijuana to relieve or treat health problems don’t discuss their substance use with their physician, according to a new study.

The study of more than 17,000 Americans ages 50 and older found almost 10% used cannabis in the past year. Almost 20% used it for a medical reason, such as depression or pain, HealthDay reports.

People who reported using cannabis for medical reasons were over four times more likely than people who used it for non-medical reasons to discuss their use with a health care professional, the study found. However, only a minority of people who used cannabis for medical reasons told their health care provider.

“Screening for and discussion of cannabis use and other behavioral health problems should be part of older adults’ routine health care,” the researchers concluded.