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

Abstract 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. Lay Summary The Perceived Stress Scale (PSS) is a widely used questionnaire designed to assess how an individual perceives recent stress in their life. It is unclear, however, the degree to which the PSS is measuring factors that are consistent within individuals versus those that fluctuate, and how these components might change when the PSS is administered repeatedly over time. To address this knowledge gap, data from two studies were used—a study of 137 patients with heart failure followed for 39 months and a study of 73 younger, healthy adults followed for 12 months. In each, participants completed up to 13 PSS assessments, with 2,880 total PSS assessments completed across the studies. Multilevel linear mixed modeling was used to examine sources of score variance across assessments. Between-person varian