Auditory vocal hallucinations (AVHs) are the most common hallucinations of psychosis and do often occur in several other mental disorders. The effects of current standard psychological therapy (cognitive behavioural therapy; CBT) for auditory vocal hallucinations are limited. Thus, there is a need to improve cognitive behavioural therapy for auditory vocal hallucinations. As for many other mental disorders specific treatments have been improved using interventions targeting mental imagery, and recent studies pointed towards an association between psychotic symptoms and mental imagery, adding imagery intervention to CBT might aid this aim.~The main objective of this study is to assess the feasibility, acceptability, and effectiveness of four imagery intervention techniques (metacognitive imagery intervention, imagery rescripting, promoting positive imagery and competing imagery task) for auditory vocal hallucinations. The investigators are primarily interested in whether these imagery intervention techniques would be associated with a decrease in auditory vocal hallucinations and imagery symptoms. Also, the investigators are interested in whether these imagery intervention techniques would be a feasible and acceptable intervention for patients with a disorder in the transdiagnostic psychosis and suffering from auditory hallucinations. Secondly, the investigators aim to assess the effects on the level of delusions, visual hallucinations and social and occupational functioning. Lastly, the investigators aim to explore the working mechanisms of imagery, affective symptomatology, and auditory vocal hallucinations by three times daily measuring these symptoms for a period of seven weeks.~The investigators hypothesise that 1) all four imagery interventions are associated with a significant decrease in AVHs (e.g., a decline in the level of auditory vocal hallucinations) and imagery characteristics (e.g., decline in imagery frequency, imagery appraisals and imagery quality), whereas no serious adverse side-effects would occur, drop-out rates of therapy are low and patients will give a good qualitative review of therapy. 2) Psychotic symptoms decrease and social and occupational functioning increase after treatment. 3) The severity of emotional imagery is positively associated with the severity AVHs. In addition, the investigators hypothesize that this association may be different for different imagery aspects, with stronger associations between imagery appraisals (i.e., the encapsulated beliefs, and metacognitive beliefs) and the severity of AVHs as compared to other imagery aspects (frequency and quality aspects). And 4) The associations between imagery related factors and the severity of AVHs are mediated by the level of symptoms of anxiety and depression.~The primary outcome variables, the level of auditory vocal hallucinations and imagery characteristics, are calculated using daily measurements during a two-week baseline, during the intervention and after the end of intervention at follow-up at 7 weeks. Most secondary outcome variables are assessed using self-report measures before baseline, and at pre- and post-intervention.
This study explores the feasibility, acceptability, and effectiveness of four imagery intervention techniques (metacognitive imagery intervention, imagery rescripting, promoting positive imagery and competing imagery task) for auditory vocal hallucinations using four single case series with an A-B-A within subject design.