Cannabis use is associated with lower retention in methadone maintenance treatment, but not among schizophrenic- and other chronically psychotic patients.
The findings of studies on cannabis use and retention in methadone maintenance treatment (MMT) are inconsistent. To study cannabis use and its relationship to patients outcomes in MMT withwithout lifetime DSM-IV-TR schizophreniachronic-psychosis diagnosis. Since June 1993, 877 patients with available lifetime DSM-IV-TR psychiatric diagnosis were followed-up until December 2017. Urine drug screens on admission and after one year were analyzed. Lifetime schizophreniapsychosis was diagnosed in 50 (5.7%) patients. They did not differ from the other 827 by admission cannabis use (18.0% vs. 12.3%) and had similar 1-year retention rates (76.0% vs.77.0%, respectively). Cumulative retention of the cohort excluding schizophreniachronic-psychosis was longer for the 667 patients who did not use cannabis after 1-year (9.1 years, 95%CI 8.4-9.9) compared with the 118 cannabis-users after 1-year (6.0 years, 95% CI 4.8-7.2, p<.001). Among the schizophreniachronic-psychosis group, cannabis was not related to retention (38 non-users, 7.9 years 95%CI 5.2-10.5 vs. 9 cannabis-users, 9.9 years, 95% CI 3.8-16.0, p.5). Survival was shorter for the 41 schizophreniachronic-psychosis non-users (15.2 years, 95% CI 12.8-17.7) than for the 719 non-schizophreniachronic-psychosis non-users (18.5, 95%CI 17.9-19.2, p 0.009). However, survival was comparable among the 9 cannabis-users with schizophreniachronic-psychosis (20.1, 95% CI 16.2-24.1) and 101 other cohort users (18.6, 95% CI 16.9-20.4). Cannabis use is associated with decreased retention among MMT patients, however the effects of cannabis on schizophreniapsychosis patients on retention and survival cannot be verified due to the small sample size and the limited data regarding chronicity of cannabis use. Future larger, prospective studies are needed.