Online MCT group (10 sessions) will be delivered by colleague CBT therapist (with previous experience of delivering MCT group) and assistant psychologist/clinical associate psychological practitioner, where all professionals will receive appropriate training by chief investigator. The group will also have one expert patient who attended the previous pilot group (at The NHS Trust) and is willing to help conduct the current MCT training. All psychology staff have experience in delivering psychological therapies and working with psychosis.

The study will use qualitative data to refine the results of the quantitative findings by using follow-up semi-structured interviews to better understand the participants' experiences who had a minimum of 40% reduction of their persecutory delusions and/or cognitive biases and/or secondary measures (CHOICE and CORE-OM 34). The interviews will be conducted immediately post-intervention.

TAU group: Treatment as usual is the general treatment protocol for patients with first episode of psychosis in the Early Intervention in Psychosis Service, where most patients have antipsychotic medication and at least monthly contact with care coordinator, and at least 6 monthly outpatient appointment with a psychiatrist.

The MCT will consist of spending 90 minutes a week in a small online group setting working through a series of workshops. Participants will also be asked to complete homework each week and they will be supported with this. Interviews and questionnaires regarding symptoms and thinking errors will be used before and immediately after the intervention. The participants who attended the group and improved in their symptoms and thinking errors will be invited to an interview asking them what worked for them and how they found the group.

This scale to measures delusional beliefs and auditory hallucinations. The scale has demonstrated excellent inter-rater, test-retest reliability (Haddock et al 1999). Furthermore, its validity has been established through research on individuals experiencing a first episode of psychosis (Drake et al., 2007).

It evaluates specific cognitive biases such as catastrophizing, dichotomous thinking, emotional reasoning, and jumping to conclusions by using thirty vignettes that depict everyday life scenarios. Participants are asked to rate the scenarios based on four response options. Peters et al. (2014) have determined that this questionnaire has good reliability and concurrent validity.

This is demonstrated in various studies such as Moritz et al. (2011), Favrod et al. (2014), Moritz et al. (2013), and Briki et al. (2014). The PANSS is a 30-item interview assessment tool designed to evaluate the intensity of psychotic symptoms and has demonstrated high interrater reliability (Kay et al., 1987).

It is an outcome measure that is used to assess the presence and severity of paranoid thoughts. It consists of 18 items and was revised by Freeman et al. in 2019. The R-GPTS is used to assess the severity of paranoid thoughts in individuals with a range of mental health conditions such as paranoia and schizophrenia. The results of the studies conducted by Freeman et al. (2019) provide evidence for the validity and reliability of the R-GPTS as a measure of paranoid thoughts. These findings suggest that the R-GPTS can be used with confidence in clinical and research settings to accurately assess the presence and severity of paranoid thoughts.

It is a widely used measure of distress in the psychology department's Early Intervention for Psychosis Service, where the researcher will conduct the study. The highest possible score on the questionnaire is 136, which indicates extreme levels of distress. It has been established as a valid measure with robust outcomes (Evans et al., 2002).