Improving physical health and reducing substance use in psychosis - randomised control trial (IMPACT RCT): study protocol for a cluster randomised controlled trial

Background: Cardiovascular morbidity and mortality is increased in individuals with severe mental illnesses. We set out to establish a multicentre, two arm, parallel cluster randomized controlled trial (RCT) of a health promotion intervention (HPI), IMPACT Therapy. The patient-tailored IMPACT Therapy aims to target one or more health behaviours from a pre-defined list that includes cannabis use; alcohol use; other substance use; cigarette smoking; exercise; diet and diabetic control, prioritising those identified as problematic by the patient, taking a motivational interviewing and CBT approach. Methods: Impact therapy will be delivered by care coordinators in the community to the treatment group and will be compared to treatment as usual (TAU). The main hypothesis is that the addition of IMPACT Therapy (HPI) to TAU will be more effective than TAU alone in improving patients' quality of life as measured by the Short Form-36, including mental health and physical health subscales on completion of the intervention at 12 months post randomisation. A subsidiary hypothesis will be that addition of IMPACT Therapy (HPI) will be more cost-effective than TAU alone in improving health in people with SMI 12 months from baseline. The IMPACT therapy patient groups' improvement in quality of life, as well as its cost effectiveness, is hypothesised to be maintained at 15 months. Outcomes will be analyzed on an intention-to-treat (ITT) basis. Discussion: The results of the trial will provide information about the effectiveness of the IMPACT therapy programme in supporting community mental health teams to address physical comorbidity in severe mental illness.