CIRCLE is a Randomised Controlled Trial testing a new treatment aimed at helping people who are currently Early Intervention Service users to reduce or stop using cannabis. The reason for testing novel interventions in treating cannabis use is that, as a recent Cochrane review concluded, no treatment has so far been found that reliably reduces cannabis use in this population group. However, cannabis use represents a significant clinical issue for clinicians. Previous research has found that using cannabis roughly doubles the likelihood of someone with a history of psychosis relapsing (Linszen et al. 1994, Hides et al. 2006, Wade et al. 2006). In addition, it is associated with increased symptom severity, poorer clinical outcomes, and longer periods of recovery. This could translate into higher medication doses and longer duration of treatment.  

Treatments that have been tried in the past include motivational interviewing, psychoeducation, and CBT (for example see the MIDAS trial, Barrowclough et al. 2010). The aim of CIRCLE is to test a Contingency Management (CM) type intervention. CM interventions have been trialled successfully for a range of different substances across many different populations (click here or here for more information about CM). However, CIRCLE is the first time CM has been trialled for cannabis use amongst people with a history of psychosis. The CIRCLE intervention is a 12 week reward scheme in which service users are rewarded with shopping vouchers if they successfully abstain from using cannabis. Alongside it we also offer participants a psychoeducation package that provides more information about the relationship between cannabis and mental health

Participants in CIRCLE are randomly assigned to one of two groups: an experimental group, which is offered both the psycho-education sessions and the reward scheme, and a control group, which is offered the psychoeducation sessions only. The aim of the trial is to investigate whether a reward scheme would be a cost-effective method for reducing cannabis use amongst Early Intervention service users. The below leaflet, aimed at potential participants for CIRCLE, briefly describes the design of the trial:


For more information you can download thetrial protocol here or a trial booklet aimed at clinicians here. Alternatively, you can speak to a member of the CIRCLE team. We have created a video of the interventions here.

CIRCLE was run as a collaboration between University College London, King's College London, University of Warwick, and University of Sussex. The Chief Investigator is Professor Sonia Johnson, Division of Psychiatry, UCL. 

Other members of the trial management group were: Steven Marwaha, Associate Clinical Professor, Warwick University; John Strang, Head of the National Addictions Centre, Institute of Psychiatry; Thomas Craig, Professor of Social Psychiatry, Institute of Psychiatry; Paul McCrone, Professor of Health Economics, Institute of Psychiatry; Michael King, Professor of Primary Care Psychiatry, UCL and Joint Director of PRIMENT Clinical Trials Unit, UCL; David Fowler, Professor of Social Psychiatry, University of Sussex; Stephen Pilling, Professor of Clinical Psychology and Effectiveness, UCL; Louise Marston, Senior Research Statistician, UCL and Priment Clinical Trials Unit, UCL; Rumana Z Omar, Professor of Medical Statistics, UCL; Mark Hinton, Manager, headspace Adelaide Youth Early Psychosis Programme.

The Trial Steering Committee was chaired by Professor Thomas Barnes, Faculty of Medicine, Imperial College London.

CIRCLE is funded by the NIHR HTA programme (09/144/50

Trial Registration: ISRCTN33576045