Psychometric evaluation of the internalized stigma of mental illness scale for patients with mental illnesses: measurement invariance across time.

Chung-Ying Lin,Chih-Yin Chen,Nori Takei,Jung-Der Wang,Chih-Cheng Chang,Tsung-Hsien Wu

doi:10.1371/journal.pone.0098767

Abstract

BackgroundThe current investigation examined the psychometric properties of the Internalized Stigma of Mental Illness (ISMI) scale in a sample of patients with mental illness. In addition to the internal consistency, test-retest reliability, and concurrent validity that previous studies have tested for the ISMI, we extended the evaluation to its construct validity and measurement invariance using confirmatory factor analysis (CFA).MethodsThree hundred forty-seven participants completed two questionnaires (i.e., the ISMI and the Depression and Somatic Symptoms Scale [DSSS]), and 162 filled out the ISMI again after 50.23±31.18 days.ResultsThe results of this study confirmed the frame structure of the ISMI; however, the Stigma Resistance subscale in the ISMI seemed weak. In addition, internal consistency, test-retest reliability, and concurrent validity were all satisfactory for all subscales and the total score of the ISMI, except for Stigma Resistance (α = 0.66; ICC = 0.52, and r = 0.02 to 0.06 with DSSS). Therefore, we hypothesize that Stigma Resistance is a new concept rather than a concept in internalized stigma. The acceptable fit indices supported the measurement invariance of the ISMI across time, and suggested that people with mental illness interpret the ISMI items the same at different times.ConclusionThe clinical implication of our finding is that clinicians, when they design interventions, may want to use the valid and reliable ISMI without the Stigma Resistance subscale to evaluate the internalized stigma of people with mental illness.

Highlights

The stigma of mental illness, unlike the stigma of other medical conditions, is still highly prevalent in most high-income countries with good healthcare [1,2]
Demographics and Internalized Stigma of Mental Illness (ISMI) scores Because 3 participants did not answer all the questions on the ISMI, all their data were excluded from analysis; only the data from the other 347 participants were analyzed
We found that the datamodel fit was acceptable for both the first- and the second-order confirmatory factor analysis (CFA) models, which suggests that the construct of the ISMI is appropriate

Summary

Introduction

The stigma of mental illness, unlike the stigma of other medical conditions (e.g., epilepsy, leprosy, and cancer), is still highly prevalent in most high-income countries with good healthcare [1,2]. People with mental illness are left feeling that they are not members of the society in which they live [7] Even those who have not experienced discrimination (the behavioral manifestation of public stigma) may feel alienated because of prejudice (the attitudinal manifestation of public stigma) [8]. Ritsher (Boyd) et al [7] call this kind of stigma ‘‘internalized stigma’’, and say that it is ‘‘one of the especially painful and destructive effects of stigma’’ Based on their definition, Ritsher (Boyd) et al [7] developed a reliable and valid instrument, the Internalized Stigma of Mental Illness (ISMI) scale for people with mental illness, and the ISMI has been broadly used in different cultures [9]. In addition to the internal consistency, test-retest reliability, and concurrent validity that previous studies have tested for the ISMI, we extended the evaluation to its construct validity and measurement invariance using confirmatory factor analysis (CFA)

Methods

Results

Conclusion