Testing the Efficacy of the Cannabis Clinic for Patients With Psychosis (CCP) Intervention for Cannabis Use Reduction/Cessation in Patients With First Episode Psychosis (FEP)

People suffering from psychosis who use cannabis experience more relapses, long and compulsory admissions, with huge costs to the individual, families and health services. The Cannabis Clinic for Psychosis (CCP) was developed to respond to this clinical need. A published review of the CCP's intervention showed its safety and efficacy in supporting people suffering from psychosis with reducing their cannabis use. Nevertheless, for the CCP model of care to be applied widely and benefit a larger clinical population, its intervention needs to be tested in a Randomised Control Trial (RCT). The proposed CCP RCT is a waiting list randomised controlled trial that aims to evaluate the clinical efficacy of the existing CCP intervention. Participants will be adults currently under the care of South London and Maudsley (SLaM) Early Intervention Teams for first onset psychosis, who are dependent on cannabis and who express an intention to reduce or stop their use. The RCT primary outcome will measure changes in all participants' cannabis use. Participants will be randomised to either the intervention group or the waiting list control group receiving Treatment As Usual (TAU). The CCP intervention comprises 12 weekly (+/- 4 weeks) one-to-one sessions, with optional participation in a weekly online peer group. Sessions are delivered by trained clinicians and include evidence-based psychosocial techniques, including Motivational Interviewing (MI), Cognitive Behavioural Therapy (CBT), SMART goal settings and support for co-occurring tobacco use. The treatment is non-pharmacological and administered via participant-led approach that accommodates online or face-to-face sessions to meet the patient preference. Qualitative data from the recent CCP proof of concept paper indicate that the flexibility in allowing patients choice on the session's modality (online/face to face, hybrid) increased and maintained engagement. The study is fully funded by the Maudsley Charity and due to last 30