Contingency management – the use of positive reinforcement in the form of supermarket vouchers to shape behaviour – makes no difference in the frequency of cannabis use or relapse rates in those with early psychosis. Although psychotic symptoms initially decrease, these changes are not sustained over the longer term and are no better than with an optimised educational intervention.
This NIHR-funded multicentre randomised controlled trial included 551 young adults who were being treated in an ‘Early Intervention in Psychosis’ service of 23 NHS trusts in the Midlands and south-east of England. It found no clinical difference in time to relapse, frequency of cannabis use, symptom severity, or engagement in education or work. The total cost of inpatient hospital admissions was slightly lower for those receiving contingency management, but the reason for this is not clear.
Why was this study needed?
Psychosis is a mental health condition that causes people to perceive or interpret things differently from those around them. Psychosis may involve hallucinations or delusions. The use of cannabis, particularly high-potency cannabis, significantly increases the likelihood of psychotic disorder compared with never users. Cannabis was the most commonly used drug in England and Wales in 2017/18. About 2.4 million adults (16 to 59 years) used it that year, including around one million young adults from 16 to 24 years old.
Contingency management, a set of techniques used to reinforce certain behaviours, has proven clinically effective and cost-effective in a variety of contexts including severe mental illness, smoking and alcohol misuse. Most contingency management research has been undertaken in the US.
This trial aimed to examine the impact of a shopping voucher reward contingency management programme on cannabis use and relapse in those with early psychosis to see if it could work in England.
What did this study do?
This trial randomised 511 people aged 18 to 36 to either a combined voucher reward contingency management and optimised psychoeducational intervention or the psychoeducation intervention alone. Contingency management rewarded self-reported abstinence from cannabis use, confirmed by urine analysis, with shopping vouchers. Vouchers began at £5 and rose by £5 every two weeks of abstinence to a maximum of £240 over 12 weeks.
The optimised psychoeducational intervention was six 30-minute sessions on the potential advantages and disadvantages of cannabis use and abstinence. Interviews, questionnaires and electronic patient records were used to determine relapse rates and background data.
A high proportion of participants did not engage in either the contingency management or psychoeducation sessions (they declined or discontinued the intervention). This lack of retention might have reduced the chance of finding a difference if one existed.
What did it find?
- Similar numbers of participants receiving the psychoeducation sessions (61%) and in the contingency arm (57%) had cannabis-positive urine at 18 months (OR 0.84, 95% CI 0.49 to 1.41). Self-reported cannabis-using days at three months and 18 months were also similar.
- Clinical outcomes were similar for readmission rate: time to admission (hazard ratio [HR] 1.03, 95% CI 0.76 to 1.40); or likelihood of at least one admission (OR 1.02, 95% CI 0.70 to 1.48).
- No variance was found in the likelihood of participant engagement in work (OR 0.95, 95% CI 0.62 to 1.46) or study (OR 0.82, 95% CI 0.50 to 1.35).
- There were mixed results for Early Intervention in Psychosis service users receiving contingency management, with lower rates of positive symptoms at three months (coefficient –0.07, 95% CI –14 to 0) but not at 18 months (coefficient –0.04, CI –0.13 to 0.05).
What does current guidance say on this issue?
The NICE 2017 guideline on drug misuse prevention advocates targeted interventions for people at risk of drug misuse. The NICE 2007 guideline on drug misuse in over 16s advocates a nationwide training programme for NHS staff in contingency management. This guideline reports that the lack of training coupled with staff, service user and public concerns about the longevity of any behavioural change, and the possibility of an intervention appearing to reward drug use, makes the introduction of contingency management in drug misuse services a challenge.
What are the implications?
Contingency management, using the current value of shopping vouchers, is not effective in reducing cannabis use or relapse in people with early psychosis.
The researchers thought that modifying the contingency management programme design or reward level may produce different outcomes. On a positive note, the number of days of cannabis use had reduced in both groups by six months which may indicate that the psychoeducation sessions were beneficial, and they suggest that this is worth exploring further.
Citation and Funding
Johnson S, Rains LS, Marwaha S et al. A contingency management intervention to reduce cannabis use and time to relapse in early psychosis: the CIRCLE RCT. Health Technol Assess. 2019;23(45).
This project was funded by the NIHR Health Technology Assessment Programme (project number 09/144/50).
NHS website. Overview: psychosis. London: Department of Health and Social Care; reviewed 2016.
NICE. Drug misuse in over 16s: psychosocial interventions. CG51. London: National Institute for Health and Care Excellence; 2007, checked July 2016.
NICE. Drug misuse prevention: targeted interventions. NG64. London: National Institute for Health and Care Excellence; February 2017.
Office for National Statistics. Drug misuse: findings from the 2017/18 Crime Survey for England and Wales. Statistical Bulletin 14/18. London: Office for National Statistics; 2018.
Rash CJ, Alessi SM, Zajac K. Examining implementation of contingency management in real-world settings. Psychol Addict Behav; 2019; doi: 10.1037/adb0000496. [Epub ahead of print].
Produced by the University of Southampton and Bazian on behalf of NIHR through the NIHR Dissemination Centre