A service evaluation of a group mindfulness-based intervention for distressing voices: how do findings from a randomized controlled trial compare with routine clinical practice?

Background: Person-based cognitive therapy (PBCT) was developed as a treatment for psychosis. The effectiveness of group PBCT was examined in the Mindfulness for Voices (M4V) randomized controlled trial and generated promising results. Group PBCT was implemented as a trans-diagnostic treatment for distressing voices within the Sussex Voices Clinic (SVC), a specialist secondary care mental health service.

Aim: To conduct a service evaluation of engagement, outcomes and cost of group PBCT within SVC, and to compare engagement and outcomes from routine practice with the M4V trial. Secondary aims were to explore predictors of levels of engagement and change in group PBCT.

Method: Service level data from 95 SVC patients were evaluated. Descriptive statistics, hypothesis tests and linear regression models were used. The primary clinical outcome was voice-related distress. Engagement levels and pre-post effect sizes were estimated; associated predictors were explored.

Results: Fifty-nine per cent of patients completed group PBCT within SVC, compared with 72% within M4V. Completers within SVC had lower baseline depression scores compared with non-completers. There were significant improvements in voice-related distress (Cohen's d = -0.47; p = 0.001), subjective recovery (Cohen's d = 0.35; p = 0.001) and depression (Cohen's d = -0.20; p = 0.044); these outcomes were comparable to M4V. Higher baseline subjective recovery and lower depression both predicted improvement in voice-related distress. Therapy within SVC cost an average of £214 per patient.

Conclusion: PBCT groups can be delivered trans-diagnostically in routine clinical practice. Engagement was lower when compared with an RCT, but outcomes were comparable. The low level of resources involved suggests that group PBCT can offer value for money.