Measuring stress in Australia: validation of the perceived stress scale (PSS-14) in a national sample.

BACKGROUND

In Australia, the stress levels have increased over the years, impacting on the physical and mental health of the general population. The aim of the present study was to evaluate the validity and reliability of the PSS-14 in an Australian population.

METHODS

The PSS-14 was applied to a large national sample comprising 3857 Australians in the population-based cross-sectional study Australia's National Survey of Adult Oral Health 2004-2006. The psychometric properties analyzed with the Rasch model and Graphical Log-linear Rasch models were: model fit, item fit, local dependence, differential item functioning, unidimensionality, reliability, targeting and criterion validity.

RESULTS

The PSS-14 did not fit the pure RM (χ2 (55) = 3828.3, p = < 0.001) and the unidimensionality of the whole scale was rejected (p = < 0.001). The Perceived Stress (χ2 (27) = 1409.7, p = < 0.001) and Perceived Control (χ2 (27) = 713.4, p = < 0.001) subscales did not fit the pure RM. After the deletion of two items, the Perceived Stress subscale (χ2 (96) = 94.4, p = 0.440) fitted a GLLRM, while the Perceived Control scale (χ2 (55) = 62.50, p = 0.224) fitted a GLLRM after the exclusion of four misfitting items.

CONCLUSIONS

The Perceived Stress subscale displayed adequate psychometric properties after the deletion of two items; however, the majority of problems centered around the Perceived Control subscale. The presence of differential item functioning among four items indicates that adjustment of total scores is required to avoid measurement bias. Recommendations for future applications in Australia are provided.