A contingency management intervention to reduce cannabis use and time to relapse in early psychosis: the CIRCLE RCT.

A large proportion of people with psychosis use cannabis, despite the negative impact that it has on their recovery. So far, a clearly effective way of helping young people in the early stages of psychosis to cut down their cannabis use has not been found. The CIRCLE trial investigated if an approach known as contingency management (CM) would be beneficial for this group. This approach involves offering voucher rewards for not using cannabis. It has been effective in addressing drug use problems in general, but there is not much evidence about its effects on cannabis use in those with psychosis. A total of 551 service users with psychosis who used cannabis agreed to enter the trial. Half of the sample group was chosen by a chance method to receive CM. The other half formed a comparison group. The CM group received shopping vouchers if urine samples showed that they had not used cannabis for the previous week, measured over 12 weekly sessions. Participants could obtain £240-worth of vouchers if they did not use cannabis during the treatment period. The participants in both groups were also offered a six-session psychoeducation programme about the pros and cons of cannabis use and ways to reduce use of it. The main comparison in the trial was the average length of time in each group before a relapse of psychosis occurred, which was recorded for each participant over 18 months after they joined the trial. The results found no difference between the two trial groups in this measure. Furthermore, there were no differences found between the groups in terms of the levels of cannabis use, clinical symptoms, or engagement with work or education. However, a cost-effectiveness analysis found an 85% chance of CM being more effective than the treatment-as-usual psychoeducation package, which appears to be because of the lower use of inpatient services by those receiving CM. However, it is difficult to understand why this was, because there was no drop in cannabis use. The results suggest that CM is unlikely to be clinically effective and that alternative treatments are still needed.