It is conventional wisdom that any substance use during drug treatment leads to lower rates of success. But a new study in the American Journal on Addictions suggests that’s not always so.

The study looked at patients in treatment for opiate dependence using a drug called naltrexone – a treatment whose effectiveness, the researchers write, “has been severely limited by poor adherence.” As part of a study designed to test two different support protocols intended to help patients stay on naltrexone treatment, researchers also looked at use of other substances by means of regular urine tests conducted during clinic visits.

Contrary to conventional wisdom, patients with “intermittent” marijuana use (defined as between 1% and 79% of urine tests coming back positive) stayed on treatment for nearly four times as long as those who abstained completely. Treatment adherence by “consistent” marijuana users (80% or more positive urine tests) was almost identical to that of the abstainers.

The researchers note that the beneficial effect was most apparent early in treatment, that marijuana use was not only associated with staying in treatment longer but also with more consistent pill-taking, and that during the study the patients tended to maintain or even increase their marijuana use. This, they write, is “consistent with a process of self-medication. These findings are of interest because they suggest the hypothesis that moderate cannabis use may be exerting a beneficial pharmacological effect improving the tolerability of naltrexone in the early weeks after induction.”