Many individuals with schizophrenia also suffer from marijuana addiction that worsens their problems related to schizophrenia. Most of the medications prescribed for schizophrenia have no effect on reducing marijuana use. Preliminary data suggests that clozapine, an atypical antipsychotic, may limit marijuana use in people diagnosed with schizophrenia, but it is not commonly used due to its side effects and is reserved for people who do not respond to other antipsychotic medications. In the proposed study, 132 individuals who are diagnosed with both schizophrenia and a cannabis use disorder will be randomized to a 12-week treatment course with either clozapine or risperidone (another commonly prescribed antipsychotic medication) to test the hypothesis that patient treated with clozapine will have decreased cannabis use as compared to patients treated with risperidone. Should this study indicate that clozapine will lessen marijuana use in persons diagnosed with schizophrenia more than risperidone, it will provide evidence needed to begin to shift clinical practice toward its use in this population.
Name: Clozapine
Description: Clozapine: target dose of 400mg per day with a maximum dose of 550mg per dayType: DrugClozapine
Name: Risperidone
Description: Clozapine: target dose of 4mg per day with a maximum dose of 6mg per dayType: DrugRisperidone
Description: Intensity of cannabis use will be assessed by the amount of cannabis consumed each week
Measure: Intensity of cannabis use Time: up to 12 weeksDescription: Frequency of cannabis use will be assessed by the days of use per week.
Measure: Frequency of cannabis use Time: up to 12 weeksDescription: Symptoms of schizophrenia will be measured using the scores on standardized assessments, including the Brief Psychiatric Rating Scale, the Schedule for the Assessment of Negative Symptoms, and the Clinical Global Inventory
Measure: Symptoms of Schizophrenia Time: up to 12 weeksDescription: Quality of life will be assessed based on scores on the Quality of Life scale and the "subjective section" from the Quality of Life Interview
Measure: Quality of Life Time: Monthly for three monthsDescription: Neuropsychological functioning will be assessed using the MATRICS Consensus Cognitive Battery;
Measure: Neuropsychological functioning Time: Every 6 weeks for three monthsDescription: We will assess reward responsiveness using the computerized Probabilistic Reward Task. This task measures the extent to which a participant biases their responding toward a more rewarded versus less rewarded stimulus consistent with the view that frequency of responding is increased toward reinforcers.
Measure: Reward responsiveness Time: Every 6 weeks for three monthsAllocation: Randomized
Parallel Assignment
There is one SNP
Finally, this study will explore whether those patients with the val/val genotype at the COMT Val158Met locus are more likely to decrease cannabis use during CLOZ treatment than are those without the val/val COMT genotype. --- Val158Met ---