AugmENtation witH cAnnabidiol iN first episode psyChosis: a doublE blind randomised controlled trial (STEP-ENHANCE Trial)

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• Individuals are excluded from participation in the trial if they meet one or more of the following exclusion criteria. Rescreening is permitted where the relevant circumstances may have changed. 1. Having been previously treated with a different antipsychotic (to the current one) at an adequate dose* for 4 weeks or longer. 2. Current or previous treatment with clozapine and/or current treatment with sodium valproate, valproate semisodium, or clobazam. In cases of current use of these medicines, participation is only permitted if they can and will be discontinued or switched to a suitable alternative medication prior to randomisation. 3. Hypersensitivity to the active substance, sesame oil, sesame seed or any of the excipients of the intervention. 4. Known hepatic insufficiency and/or transaminase elevations levels exceeding the upper limit of normal 2 times or more and bilirubin greater than 1.5 times the upper limit of normal. 5. Previous neurosurgery or neurological disorder, including epilepsy, which may affect the study procedures**. 6. IQ <70 as measured by a validated IQ test e.g. Wechsler Abbreviated Scale of Intelligence (WASI), Wechsler Adult Intelligence Scale (WAIS), and Wechsler Intelligence Scale for Children (WISC), as approved for local languages and appropriate for the participant’s age. 7. Pregnancy or breastfeeding. 8. The patient has a current diagnosis of ‘Substance or medication induced psychotic disorder’ or ‘Psychotic disorder due to another medical condition’ as determined through the SCID-5-RV. 9. Current active suicidal ideation within the last 2 weeks, defined as a score of 1 or higher on CDSS question 8, followed by an assessment by the treating clinician who determines it is not safe for the patient to participate in the study. 10. Meeting DSM-5 criteria for substance use disorder, with the exception of nicotine use disorder (mild, moderate, and severe allowed). Mild cannabis use disorder is allowed (i.e. can meet up to but no more than 3 criteria on the SCID) as long as the subject patient has not consumed cannabis on average more than three times a week in the past 30 days. Mild alcohol use disorder is also allowed. 11. Patient has participated in another clinical trial in which they received an experimental or investigational drug or agent within 3 months before Visit 0. Patients who have participated in Type A studies (e.g. trials of standard and within-label treatments including antipsychotic medication) or non CTIMP studies (e.g. studies of exercise therapy) must have completed the intervention but may be included if permitted by the protocol of the other trial. 12. The participant refuses any mandatory safety checks during the trial, specifically, refusal of: urine pregnancy test (those of child-bearing potential only); safety blood test; reporting of adverse events; and assessment of suicidality. 13. Any other significant disease or disorder which, in the opinion of the Investigator, may either put the participants at risk because of participation in the trial, or may influence the result of the trial, or the participant’s ability to participate in the trial. *Adequate doses are provided in Appendix B. **Minor neurological disorders such as migraine, other minor headache disorders, sleep disorders or nerve palsies which are unlikely to affect study outcomes including neuroimaging measures are permitted.