Semi-structured Interview Measure of Stigma (SIMS) in psychosis: Assessment of psychometric properties

Abstract

Stigma is a significant difficulty for people who experience psychosis. To date, there have been no outcome measures developed to examine stigma exclusively in people with psychosis. The aim of this study was develop and validate a semi-structured interview measure of stigma (SIMS) in psychosis. The SIMS is an eleven item measure of stigma developed in consultation with service users who have experienced psychosis. 79 participants with experience of psychosis were recruited for the purposes of this study. They were administered the SIMS alongside a battery of other relevant outcome measures to examine reliability and validity. A one-factor solution was identified for the SIMS which encompassed all ten rateable items. The measure met all reliability and validity criteria and illustrated good internal consistency, inter-rater reliability, test retest reliability, criterion validity, construct validity, sensitivity to change and had no floor or ceiling effects. The SIMS is a reliable and valid measure of stigma in psychosis. It may be more engaging and acceptable than other stigma measures due to its semi-structured interview format.

Introduction

Many outcome measures have been developed to assess the impacts of stigma on service users diagnosed with a serious mental illness (SMI). However, a recent systematic review of individual outcome measures of stigma identified that all of the available measures are self-report measures and not specific to psychosis (Brohan et al., 2010). Brohan et al. (2010) identified that the three most widely-used self-report measures of stigma were; the Perceived Devaluation and Discrimination Scale (PDD; Link, 1987), the Internalised Stigma of Mental Illness Scale (ISMI; Ritsher et al., 2003), and the Self-Stigma of Mental Illness Scale (SSMIS; Corrigan et al., 2006). Brohan et al. (2010) identified that these outlined measures each lacked some form of reliability and validity; for example, none met requirements for floor and ceiling effects. Furthermore, as stated, these measures were developed for use with individuals experiencing SMI. Arguably not all SMI's are comparable in terms of their experiences of stigma which will also hinder reliability and validity of stigma measures. For example, those with a schizophrenia spectrum disorder are viewed most negatively by the public (Crisp et al., 2005, Wood et al., 2014), are most discriminated against (Dinos et al., 2004, Thornicroft et al., 2009), have the most intense internalised stigma beliefs, experience the worst social exclusion and have significantly lower levels of functioning, compared to those with a diagnosis of bipolar disorder and depression (Karidi et al., 2015, Oliveria et al., 2015).

The aim of this study was to develop a reliable and valid semi-structured interview measure of stigma in psychosis, in consultation with service users, which can be used to assess and monitor change in the impacts of stigma in psychosis. A semi-structured interview measure also provides diversity in a saturated pool of self-report measures. Furthermore, the semi-structured format of the interview measure offers the flexibility in questioning to identify culturally specific aspects of stigma, the lack of which has been a criticism of existing self-report measures (Semrau et al., 2015). Outcomes on the semi-structured interview measure of stigma (referred to henceforth as the SIMS) were compared to the ISMI (Ritsher et al., 2003) and Stigma Scale (King et al., 2007) to examine its ability to measure stigma. Furthermore, it was also compared to outcome measures of self-esteem, depression, hopelessness, shame and recovery, since research indicates that these psychological variables are also related to stigma and thus assist with validation (Birchwood et al., 2007, Corrigan et al., 2006, Link et al., 2001, Livingston and Boyd, 2010, Michail and Birchwood, 2013, Rüsch et al., 2014). The psychometric properties of the SIMS were examined and it was hypothesised that there will be good validity in comparison to other relevant measures. Specifically, it was hypothesised that the SIMS will be positively correlated with existing measures of stigma, and with measures of depression, hopelessness and shame, and negatively correlated with measures of self-esteem and recovery.