A method to achieve extended cannabis abstinence in cannabis dependent patients with schizophrenia and non-psychiatric controls

Background: Cannabis use disorders (CUD) are common in schizophrenia (~ 25%) compared to the general population (~ 3%). Tetrahydrocannabinol (THC), the principal psychoactive component in cannabis is fat-soluble, resulting in an extended period for cannabinoid elimination. While detection of cannabinoids in urine is indicative of prior cannabis exposure, time of last use is difficult to verify sustained abstinence for extended periods (e.g., 28-days) in chronic cannabis users. Therefore, we evaluated the utility of a sustained cannabis abstinence paradigm in patients with schizophrenia and non-psychiatric controls. Methods: Cannabis dependent patients (n = 19) and controls (n = 20) underwent 28-days of monitored cannabis abstinence facilitated with contingency management. Urine samples were taken twice weekly. Abstinence was evaluated using 1) Self-report; 2) Qualitative biochemical confirmation using MEDTOX; and 3) in a subset of participants (schizophrenia, n = 13; controls, n = 13) gas chromatography-mass spectrometry (GC-MS) was performed to obtain quantitative creatinine-normalized carboxy-THC (THC-COOH) metabolite levels < 20 ng/mL). Subjective assessments were used to assess behavioral correlates of cannabis abstinence and further supported time-dependent abstinence trajectories. Results: Abstinence rates of 42.1% (8/19) in patients and 55% (11/19) in controls (p = 0.53) were observed. Increased cannabis withdrawal symptoms in both patients and controls supported abstinence. Discussion: Our results suggest a feasible method for identification of short-term cannabis abstinence in individuals with schizophrenia at rates comparable to controls. Monitoring sustained abstinence may have implications for potential interventions for CUDs in schizophrenia.