The Perceived Stress Scale as a Measure of Stress: Decomposing Score Variance in Longitudinal Behavioral Medicine Studies.

BACKGROUND:The Perceived Stress Scale (PSS) is a widely used measure designed to assess perceptions of recent stress. However, it is unclear to what extent the construct assessed by the PSS represents factors that are stable versus variable within individuals, and how these components might vary over time. PURPOSE:Determine the degree to which variability in repeated PSS assessments is attributable to between-person versus within-person variance in two different studies and populations. METHODS:Secondary analyses utilized data from two studies with up to 13 PSS assessments: An observational study of 127 patients with heart failure followed over 39 months (Study 1), and an experimental study of 73 younger, healthy adults followed over 12 months (Study 2). Multilevel linear mixed modeling was used to estimate sources of variance in the PSS total and subscale scores across assessments. RESULTS:Between-person variance accounted for a large proportion of the total variance in PSS total scores in Study 1 (42.3%) and Study 2 (51.1%); within-person variance comprised the remainder. Between-person variance was higher for shorter assessment periods (e.g., 1 week), and was comparable when examining only the first 12 months of assessments in each study (52.9% vs. 51.1%). CONCLUSIONS:Within two samples differing in age and health status, between-person variance accounted for approximately half of the total variation in PSS scores over time. While within-person variance was observed, the construct assessed by the PSS may substantially reflect a more stable characteristic of how an individual perceives stressful life circumstances than previously appreciated.