• Nahathai Wongpakaran, Tinakon Wongpakaran, Manee Pinyopornpanish, Sutapat Simcharoen, Chawisa Suradom, Pairada Varnado, and Pimolpun Kuntawong.
• Department of Psychiatry, Faculty of Medicine, Chiang Mai University, Thailand.
• Br J Health Psychol. 2020 May 1; 25 (2): 233-256.

ObjectiveThe UCLA Loneliness Scale, containing 20 items, is one of the commonly used loneliness scales. Some shorter versions have been developed using factor analysis. The study aimed to shorten the UCLA Loneliness Scale using Rasch and factor analysis methods and test the psychometric properties of the new scale.MethodsThe full sample of the study included 719 respondents, divided into three subsamples (205, 324, and 190 for samples 1-3, respectively). The original, 20-item Revised UCLA Loneliness Scale (R-ULS) was shortened using 205 students (sample 1); the shortened scale was then validated for construct and concurrent validity with 324 students (sample 2) and 190 clinical participants (sample 3). Confirmatory factor analysis and Rasch analysis were used for construct validity. Convergent, discriminant, and concurrent validity were assessed by exploring the correlation with other psychological measurements.ResultsIn sample 1, the R-ULS was shortened to a 6-item scale (RULS-6) that fits the Rasch model. The RULS-6 met the criteria of unidimensionality and local independence without differential item functioning due to age and sex, and good targeting the clinical sample. Person Separation Index (PSI) reflected that reliability from the Rasch perspective was acceptable. However, collapsing categories 2 (sometime) and 3 (rarely) may be required in a clinical sample. When tested in samples 2 and 3, the RULS-6 fits the Rasch measurement model. Convergent and discriminant validity were demonstrated with interpersonal problems and attachment scales. As expected, a positive correlation was found between RULS-6 and anxiety, depression subscale, interpersonal difficulties, and somatization subscales denoting concurrent validity. Cronbach's alpha of the RULS-6 was good (.83).ConclusionUsing Rasch analysis, the proposed RULS-6 constituted a 70% reduction of the number of original items, yet preserved the psychometric properties in independent samples of students and psychiatric outpatients. Statement of contribution What is already known on this subject? The UCLA Loneliness Scale is a common instrument used to gauge loneliness levels. The 20-item revised scale (R-ULS) has acceptable psychometric properties but its construct varies. Due to the length of the questionnaire, administration of R-ULS is not always practical. Short versions vary in items and were developed with classic test theory (e.g., factor analysis). Rasch analysis - providing more accuracy based on measurement theory - could be used instead. What does this study add? Using a Rasch analysis approach, a 6-item scale of loneliness (RULS-6) was created. The RULS-6 was tested in student and clinical samples, meeting Rasch measurement model criteria. The RULS-6 showed promising psychometrics to be used in both non-clinical and clinical samples.© 2020 The British Psychological Society.

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