The number of teenagers and young adults going to the emergency room at Children’s Hospital Colorado for what appears to be marijuana-related reasons increased significantly after legalization, a new study by a Children’s doctor found. Dr. Sam Wang said his study contrasts with surveys that suggest youthful marijuana use in Colorado has not increased since legalization. Wang gathered data on marijuana-related emergency-room visits to Children’s Hospital and its satellite clinics for teenagers and young adults no older than 20 by looking at two measures.

The first is a hospital billing code used on a patient’s chart when marijuana is involved in a patient’s medical problem. Wang said marijuana might not be the primary reason the patient went to the hospital, but marijuana usually has to be connected to the patient’s symptoms to warrant the code being written down. The second measure is when a patient has a urine drug screen that comes back positive for marijuana. Such drug screens occur when a patient ingested an unknown substance or before a patient undergoes a psychiatric evaluation. Collecting those numbers, Wang said he found that 106 teens and young adults visited Children’s emergency room for marijuana-related reasons in 2005 and that number jumped to 631 in 2014.