FLORENCE, Italy — Cannabis use increases the risk for nonadherence to antipsychotic medications, suggesting that discouraging cannabis use may improve not only treatment adherence but also the prognosis of psychosis patients, say United Kingdom investigators.

The researchers found that cannabis use more than doubles the risk for nonadherence to antipsychotics and that continued use of the drug increases the risk for nonadherence more than fivefold.

Enrico Foglia, from the Institute of Psychiatry, Psychology and Neuroscience at King's College London, United Kingdom, toldMedscape Medical News that this is the first meta-analysis of the relationship between cannabis use and antipsychotic medication nonadherence.

The findings were presented here at the Schizophrenia International Research Society (SIRS) 2016 Biennial Meeting.

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The strength of the association, which was consistent across the studies, did not come as a surprise, inasmuch as it is known that antipsychotic nonadherence is "a big problem, and it's very prevalent,...