Background: Cannabis is the most prevalent illicit substance among people with psychosis, and its use is associated with poorer clinical and social outcomes. However, so far, there has been limited evidence that any treatment is effective for reducing use. Contingency management (CM) is an incentive-based intervention for substance misuse that has a substantial evidence base across a range of substances and cohorts. However, to date there have been no randomised controlled trials (RCTs) of CM as a treatment for cannabis use specifically in psychosis.
Objective: To conduct a RCT investigating the clinical effectiveness and cost-effectiveness of CM in reducing cannabis use among Early Intervention in Psychosis (EIP) service users.
Design: The CIRCLE (Contingency Intervention for Reduction of Cannabis in Early Psychosis) trial was a rater-blinded, multicentre RCT with two arms. Participants were randomised 1 : 1 to either an CM arm, in which participants received CM for cannabis use alongside an optimised treatment-as-usual programme including structured psychoeducation, or a control arm in which participants received the treatment as usual only.
Setting: EIP services across the Midlands and the south-east of England.
Participants: The main eligibility criteria were EIP service users with a history of psychosis, aged 18-36 years, and having used cannabis at least once per week during 12 of the previous 24 weeks.
Intervention: The CM intervention offered financial incentives (i.e. shopping vouchers) for cannabis abstinence over 12 once-weekly sessions, confirmed using urinalysis. The maximum value in vouchers that participants could receive was £240.
Main outcome measures: The main outcome was time to relapse, operationalised as admission to an acute mental health service or hospital. The primary outcome was assessed at 18 months post inclusion using electronic patient records. Secondary outcomes assessed the clinical effectiveness and cost-effectiveness of the intervention, for which data were collected at 3 and 18 months.
Results: A total of 278 participants were randomised to the CM arm and 273 were randomised to the control arm. In total, 530 (96%) participants were followed up for the primary outcome. There was no significant difference in time to admission between trial arms by 18 months following consent (hazard ratio 1.03, 95% confidence interval 0.76 to 1.40). There were no statistically significant differences in most secondary outcomes, including cannabis use, at either follow-up assessment. There were 58 serious adverse events, comprising 52 inpatient episodes, five deaths and one arrest.
Limitations: Participant retention was low at 18 months, limiting the assessment of secondary outcomes. A different CM intervention design or reward level may have been effective.
Conclusions: The CM intervention did not appear to be effective in reducing cannabis use and acute relapse among people with early psychosis and problematic cannabis use.
Future work: Cannabis use is still a significant clinical concern in this population. A pressing need remains to identify suitable treatments. A wider perspective on the social circumstances of young people with psychosis may be needed for a successful intervention to be found.
Trial registration: Current Controlled Trials ISRCTN33576045.
Funding: This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 23, No. 45. See the NIHR Journals Library website for further project information.
Keywords: CANNABIS; CONTINGENCY MANAGEMENT; EARLY INTERVENTION; FINANCIAL INCENTIVES; PSYCHOSIS; SUBSTANCE MISUSE.
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.