Recreational cannabis is legal in 10 states and Washington, DC, but regulations regarding potency do not exist. The results of a new study, led by an Iowa State University researcher, may prompt states to reconsider.

Higher average potency cannabis at first use increases the risk for the first symptom of cannabis use disorder within a year of use, according to the study published in the journal Drug and Alcohol Dependence. Brooke Arterberry, assistant professor of psychology, says this is a concern given that THC—one of the chemicals that determines potency—has increased significantly, from 3.5% in 1994 to 12.3% in 2012.

Arterberry and colleagues at the University of Michigan and Brown University found individuals whose first use cannabis at a national average 4.9% THC had 1.88 times higher risk for first cannabis use disorder symptom, while those whose first cannabis use was an average 12.3% THC were at 4.85 times higher risk. The study is specific to the first symptom and not diagnosis of the disorder, which requires two or more symptoms.

Understanding the relationship between potency and the first symptom may provide opportunity for early intervention and prevention, Arterberry said. Symptoms of the disorder may include craving or strong desire to use cannabis, recurrent use in situations in which it is physically hazardous, or failing to meet obligations at work, home or school because of recurrent use.