Experts Learning Much About Cannabis-Use Disorders
Several behavioral strategies have shown effectiveness in helping patients quit cannabis use, and some medications appear to merit further clinical research.
Marijuana is the most widely used illegal substance in the United States, with 15 million or more current users, and approximately 10 percent of these users develop cannabis-use disorders, epidemiological data have shown. The extent of this problem for clinicians was evident at a symposium on cannabis-use disorder, as the session attracted a full house of attendees at APA's annual meeting in New Orleans in May.
It is often difficult to conduct and interpret epidemiological studies of the adverse consequences and risks of marijuana use, David Gorelick, M.D., Ph.D., chief of the Pharmacotherapy Section in the Intramural Research Program at the National Institute for Drug Abuse (NIDA), told the attendees.
The observed outcomes of chronic use are influenced by many factors, including genetic variations, differences in the potency of and cumulative exposure to marjuana use, concurrent use of other substances such as tobacco and alcohol, comorbid psychiatric conditions, and psychosocial risk factors.
Growing evidence supports a link between marijuana use and psychosis, said Gorelick, citing population research from the United Kingdom. The link appears to be particularly strong with early exposure to marijuana in adolescence. Epidemiological research by Stanley Zammit, Ph.D., M.B., of Cardiff University estimated that the effect size of this link translates to this: stopping approximately 3,000 cases of cannnabis-use disorder might prevent one case of schizophrenia.
Research so far has shown no association between in-utero exposure to marijuana and the development of psychotic disorders later in life, according to Gorelick. However, two longitudinal studies using brain imaging found subtle differences in brain activities during executive-function tests between young adults with and without in-utero exposure to marijuana, even though their performance did not differ.
Meanwhile, patients with schizophrenia have reported a high rate of cannabis use—up to 50 percent in some studies, Gorelick noted. Marijuana smoking in these patients is associated with significantly worse psychotic symptoms, poorer treatment compliance, and exacerbated metabolic side effects from antipsychotic medications. “It's clearly bad for them,” he said. “The question is why they use marijuana—and there is no clear answer.”
According to recent research, physical effects of long-term cannabis use are somewhat different from those of tobacco smoking, Gorelick pointed out. Respiratory symptoms such as cough, phlegm, and wheezing have been reported. The association with chronic obstructive pulmonary disease, lu
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