Multiple sclerosis (MS) is a progressive disease characterized by neurological symptoms and sometimes heightened levels of distress. The Perceived Stress Scale (PSS) is often used in MS samples to measure stress but has not been validated in this population. Participants ( ) completed the PSS as well as measure of depression, anxiety, and mental and physical health. Factor analyses indicated that the general factor of a bifactor model accounted for a large amount of the variance in the 14-item and 10-item versions of the PSS. The 4-item PSS had two factors, the Stress subscale and the Coping subscale, but a one-factor model also fits the data well. Total scores and both subscales had sufficient reliability and validity for all versions of the PSS, although a few items of the 14-item PSS had low item-total correlations. This study supports the use of the total score of the PSS in MS but also suggests that the 10-item PSS had better psychometric properties than the 14-item PSS. 1. Introduction Multiple sclerosis (MS) is a neurological disease characterized by numbness, weakness, fatigue, vision problems, and spasticity and is often progressive [1]. People with MS often experience depression and anxiety, with as many as 50% of people with MS experiencing depression in their lifetime [2]. A common trigger of depression is stress [3], which can be defined objectively as stressful life events such as divorce or subjectively as perceptions of stress including perceptions that events are uncontrollable and unpredictable. One of the most common measures of subjective experiences of stress is the Perceived Stress Scale [4]. However, despite its use to measure perceived stress in MS [5, 6], this scale has not been psychometrically validated in this population. The Perceived Stress Scale (PSS) measures the level to which a respondent considers his or her life stressful and was designed to assess how unpredictable and controllable a person appraises his or her life [4]. The original version had 14 items, seven negatively stated and seven positively stated. Two short forms are available, one with 10 items (six negatively stated and four positively stated items) and the other with four items (two negatively stated and two positively stated) [7]. The PSS is related to health behaviors such as smoking [8] as well as depression and anxiety [9]. Other measures of stress also are related to the PSS, supporting validity [10]. The 14-item and 10-item versions showed adequate internal consistency although the 4-item version had marginal reliability, such as a Cronbach’s alpha
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