Because marijuana stimulates reward areas in the brain, people who smoke marijuana may find it more difficult to stop using other drugs and alcohol, a new study suggests.
Researchers say the findings point to the possibility that addressing marijuana use during addiction treatment could improve treatment outcomes.
They note that marijuana theoretically could have a helpful or harmful influence on achieving sobriety: substituting a less harmful drug might help to achieve abstinence from other drugs. On the other hand, continued use of an addictive drug such as marijuana could interfere with efforts to quit other drugs, or have no impact at all.
Prior studies have lent some support for each of those possibilities.
For the new study, researchers recruited more than 500 participants with opioid, cocaine, and alcohol use disorders, primarily from an inpatient detoxification unit. They found that marijuana use was associated with a 27 percent reduction in the odds of abstinence from drug and heavy alcohol use.
One recent study found that pre-treatment marijuana use favorably influenced abstinence rates in cocaine users, compared to no pre-treatment marijuana use. But other studies have shown that marijuana use is associated with worse treatment outcomes in patients undergoing opioid agonist treatment. And still other research has found alcohol and marijuana use to be independent of one another.
The authors say they hoped their findings might help to clarify the conflicting evidence.
“Our study followed participants over a year and included laboratory testing for drugs and alcohol, and analyses adjusted for addiction severity—making it likely that the association between marijuana use and other drug and heavy alcohol use is real,” says study leader Richard Saitz, chair of community health sciences at Boston University’s School of Public Health and professor of medicine at the School of Medicine.
“The findings might be useful for prognosis—so patients and clinicians alike can be aware that marijuana use in this circumstance increases the risk of subsequent other drug use. They are also useful because of implications for treatment or self-change. They imply that continued use of marijuana is not harmless,” says Saitz.
Saitz says that use of marijuana might increase the risk for other drug use because, like nicotine, it “stimulates the same reward pathways” in the brain.
“Continuing to stimulate those pathways with any drug could be related to using other drugs, some of which are more potent and harmful, as has been found for cigarette smoking,” he says.
The National Institutes of Health supported the research, which was published in the journal Drug and Alcohol Dependence.
<Marijuana use and achievement of abstinence from alcohol and other drugs among people with substance dependence: A prospective cohort study>, Published on Journal <Drug and Alcohol Dependence> in June 2014