In the first out-of-laboratory study to examine what happens to chronic marijuana users when they stop using the drug while continuing their normal daily activities, McLean Hospital researchers have identified withdrawal symptoms that were significant in 60 percent of participants.
In the November issue of Experimental and Clinical Psychopharmacology, the researchers report increases in irritability, anxiety and physical tension, as well as decreases in appetite and mood, among chronic users who abstained from marijuana during the four-week study.
"Most people think marijuana is a benign drug, and there is disagreement in the scientific community about whether withdrawal causes significant symptoms. This study shows that using marijuana for a long time has consequences," says Elena M. Kouri, Ph.D., associate director of McLean's Behavioral Psychopharmacology and lead author of the paper.
Previous research done at McLean and in other laboratories showed that marijuana could create dependence in users. Anecdotal case studies and evidence from studies done under laboratory conditions also indicated people suffered withdrawal symptoms when they stopped smoking marijuana.
Marijuana is the most commonly used illegal drug in the United States. Fourteen percent of adolescent and seven percent of adult marijuana users are dependent on the drug.
The McLean study included men and women between the ages of 30 and 55 who were recruited through newspaper advertisements and then interviewed at length. Thirty current users and 30 people who served as controls completed the 28-day study.
Symptoms of withdrawal first appeared in chronic users within 24 hours. They were pronounced for the first 10 days of the study. Increases in irritability and physical tension were observed in chronic users for all 28 days of abstinence.
The study raises a number of questions that can be answered only after further research. Since irritability and tension continued for 28 days, it may be that these symptoms reflect characteristics of study participants and were not really symptoms of withdrawal. The research also excluded people with psychiatric diagnoses, like depression, or who were currently taking other illicit drugs.