A new study of teens treated at an outpatient substance abuse clinic found many showed symptoms of marijuana withdrawal.

Marijuana was the substance used most often by 90 of the 127 teens in the study, HealthDay reports. Of those teens, 84 percent were considered to be dependent on marijuana, and about 40 percent experienced symptoms of withdrawal when they stopped using marijuana—a sign of drug dependence, the authors said.

“As more people are able to obtain and consume cannabis legally for medical and, in some states, recreational use, people are less likely to perceive it as addictive or harmful,” study co-author John Kelly of Massachusetts General Hospital’s Center for Addiction Medicine, said in a hospital news release.”But research shows that cannabis use can have significant consequences, and we know that among adolescents it is second only to alcohol in rates of misuse.”

Teens who had marijuana withdrawal symptoms were more likely to experience negative consequences, such as problems with school, work, relationships or finances. They were also more likely to meet criteria for marijuana dependence and mood disorders, the researchers wrote in the Journal of Addiction Medicine.

Teens who recognized and accepted that they had a substance abuse problem related to their marijuana use were more likely to make progress toward becoming abstinent, compared to those who did not think they had a problem.

“The importance of understanding the addictiveness, risks and harms associated with cannabis use is a major theme of this study’s findings,” said Kelly. “Recognizing those risks is known to reduce the likelihood that someone will start to use drugs, and better understanding of the role of substances in the problems experienced by patients may help them cut down on future use. Unfortunately, the general trend in attitudes in the U.S. is to minimize the risks and not recognize the addictiveness of cannabis.”