CHAMPAIGN, Ill. -- Heavy users of cannabis who experience withdrawal symptoms such as nervousness and cravings when they quit are likely to use again sooner than their peers, a new study finds.
Researchers at the University of Illinois found that 85 percent of people who met the criteria for a diagnosis of cannabis withdrawal during their intake assessment for treatment lapsed and used cannabis again within about 16 days, while other individuals stayed abstinent about 24 days before using again, said lead author Jordan P. Davis, a doctoral student in the School of Social Work.
The 110 young adults in the study sample were near-daily users who consumed cannabis on average about 70 of the 90 days prior to entering drug treatment. Participants who experienced withdrawal symptoms reported an average of two symptoms, such as mood disturbances (48 percent), difficulty sleeping (40 percent) and restlessness (33 percent), according to Davis and co-author Douglas C. Smith.
Whether cannabis use leads to physiological dependence and withdrawal symptoms when users quit has been a topic of fiery debate for years among people who oppose -- and those who favor -- more liberal marijuana laws, said Smith, a professor of social work and an expert on substance abuse issues.
For the first time, the American Psychiatric Association included a code for cannabis withdrawal in the Diagnostic and Statistical Manual of Mental Disorders when it published the fifth and most recent volume of the manual in May 2013, Smith said.
Withdrawal symptoms typically begin within one to two days after a heavy user abruptly stops, and a patient must report experiencing at least three symptoms to be diagnosed with cannabis withdrawal under the DSM-5's criteria, Smith said.
A major implication from this study is that reducing the waiting time between users' initial assessment and the start of treatment could be highly beneficial for cannabis users who are experiencing withdrawal, Davis said. Immediate treatment that helps former users cope with withdrawal symptoms could help extend the period that they stay off marijuana.
"For people to be included in the study sample, they had to be using at least 45 days out of 90 days prior to entering treatment and had to have made an attempt during the preceding week to quit or cut down," Davis said. "So they are what we would consider a pretty severe population. However, we excluded people who used other illicit drugs or who were binge drinkers, to ensure that any withdrawal symptoms reported by our participants could be attributed to cannabis and not to other substances."
More than half -- 53 percent -- of the participants had been diagnosed with lifetime cannabis use disorder, indicating that they had incurred serious social and medical consequences from using the drug, including intense cravings and increased tolerance for it, Smith said.
"Prior studies have found that it's very rare for marijuana users to have physiological withdrawal symptoms, such as the muscle aches or delirium tremens" that severe alcoholics or heroin users experience when they quit, Davis said. "With cannabis, we know that the symptoms are mainly psychological and very short-lived, typically lasting from two to seven days."
"Marijuana is tricky because it stays in your body so long," Smith said. "Highly addictive substances such as heroin have short half-lives and leave the body quickly, whereas marijuana is stored in the fat cells and can be excreted in a person's urine for up to a month -- or even longer if you're a heavy user."
Marijuana's long half-life and users' reports of primarily psychological withdrawal symptoms have fueled the longstanding controversy among clinicians and researchers about whether physiological dependency and withdrawal symptoms actually occur.
"This study shows that people who met the new criteria for marijuana withdrawal in the DSM-5 had a harder time initiating abstinence, so we do need to be concerned about people who are telling us they have these withdrawal symptoms when they first try to quit," Smith said.
Most of the cannabis users in the study were being treated as outpatients. Heavy users of the drug often have familial histories of substance abuse, which may increase their difficulty of staying abstinent, the researchers said.
Funded by a grant from the National Institute on Alcohol Abuse and Alcoholism, the study was published in the Journal of Drug Issues.