|The so-called "cannabis withdrawal syndrome" is real and should be added to diagnostic manuals.|
So asserted Deborah Hasin, Ph.D., of Columbia's Mailman School of Public Health at the American Psychiatric Association meeting here.
Dr. Hasin based her conclusion on data gleaned from the landmark National Epidemiologic Survey on Alcohol and Related Conditions (NESARC), a national longitudinal study of more than 43,000 Americans with respect to their alcohol and drug use, conducted in 2001 and 2002.
"Cannabis withdrawal at this point really should be added to the DSM-V and the ICD-11," she said. The Diagnostic and Statistical Manual of Mental Disorders, now in its fourth edition, is being revised. The International Classification of Diseases (ICD) is established by the World Health Organization.
Among the questions asked in structured interviews were a number about after-effects of drug use, and Dr. Hasin and colleagues examined the answers from 2,6113 participants who identified themselves as having used marijuana three or more times a week during their period of heaviest drug use.
The most common side-effects after stopping marijuana use were feeling weak or tired, yawning, hypersomnia, psychomotor retardation, and anxiety and depression, Dr. Hasin said.
Many of those participants also used other drugs, Dr. Hasin said, so to avoid confounding, the researchers restricted their analysis to 1,119 people who used marijuana heavily—more than three times a week—but didn't indulge in binge drinking or use other drugs heavily.
The sub-population included some very heavy users—two-thirds smoked the drug between five and seven days a week, and a similar proportion smoked at least one joint a day, she said.
The same set of symptoms appeared, Dr. Hasin said, indicating that other drugs were not causing them.
Using factor analysis, the researchers classed the major symptoms into two clusters—slowness, which included sleeping more, feeling weak or tired, and yawning, and depression/anxiety, which included sweating/heart beating, anxiety, restlessness, insomnia, depression, muscle aches, and shaking.
Two key questions, she said are whether the symptoms cause distress or impairment and whether the participants turned to other drugs or returned to marijuana to avoid the distress. A negative binomial regression analysis showed that:
Both symptom clusters were associated with distress or impairment. The association was significant at P<0.01. And both were associated with using drugs to avoid the distress, again at P<0.01.
Both symptom clusters were associated with heavy use, at P<0.05, but not with the age at which participants started using the drug, Dr. Hasin said. The duration of the period of heaviest use was associated with the anxiety cluster but not with slowness, the researchers found.
Dr. Hasin said the epidemiological approach allowed the researchers to overcome problems that had dogged earlier studies of the issue, including such things as small numbers, unrepresentative samples, and confounding by other drug use.
But that may not be enough to claim that the symptoms seen are true withdrawal, said Nicholas Seivewright, M.D., a consultant psychiatrist with the Community Health Sheffield NHS Trust in Great Britain and author of Community Treatment of Drug Misuse.
Citing the case of benzodiazepines, Dr. Seivewright noted that the central argument for a withdrawal syndrome with those drugs was the emergence of novel symptoms that patients had not previously had but incurred after stopping. In the case of marijuana, he said, "I'm a bit concerned about how you can call these withdrawal symptoms" without knowing that they aren't a rebound effect or part of a pre-existing condition.
Dr. Hasin may be "jumping the gun" in labeling her symptom clusters cannabis withdrawal, he said in an interview.