Measurement invariance of the Perceived Stress Scale across race, sex, and time, and differential impacts on cocaine use treatment outcomes

Introduction

To understand the influence of phenotypic characteristics, such as stress, on substance use treatment outcomes, measures must function equivalently across groups to allow for interpretable comparisons of effects. The present study evaluated measurement invariance of the Perceived Stress Scale (PSS) across race, sex, and time, examined its association with cocaine use disorder (CUD) treatment outcomes, and tested whether associations were moderated by race and/or sex.

Methods

Data from four clinical trials evaluating behavioral and/or pharmacological treatments for cocaine use were combined providing a total sample of 302 participants with DSM-IV cocaine abuse/dependence (57.6 % Black, 42.4 % White, 43.7 % females, M_age = 40.22 years, SD = 9.26).

Results

Factor analyses support a two-factor model (i.e., general stress, self-efficacy to cope with stressors) that demonstrated configural, metric, and scalar invariance across race and sex and configural and metric invariance across time. End-of-treatment stress and coping were both related to treatment outcomes, but not treatment retention. Interactions between baseline and end-of-treatment stress and coping self-efficacy with race and sex predicting treatment retention and outcomes were not significant.

Conclusions

Results support the utility of the PSS to examine between-group differences among individuals with CUD and suggest that sociodemographic groups differ in the extent to which stress and self-efficacy to cope influence treatment outcomes.