Validation of the Symptoms of Illness Checklist (SIC) as a tool for health psychology research.

We developed the Symptoms of Illness Checklist (SIC) to study psychological influences on physical symptoms of illness. A total of 520 participants completed the SIC and, in some samples, the Salient Stressor Impact Questionnaire, Perceived Stress Scale, Daily Hassles and Uplifts Scale, Derogatis Stress Profile, Life Experiences Survey, and the Symptoms CheckList-90-R. The SIC's test-retest, internal reliability, and validity verified by physician ratings, were very good. SIC correlations with diverse stress measures were less inflated than those of other instruments indicating the SIC is a reliable and valid tool to study psychological influences on physical illness.

Controlling for occasion-specific effects when assessing the test-retest reliability of self-report health questionnaires.

OBJECTIVE: This study proposes a method for self-report health questionnaires to adjust test-retest reliability for changes during the test-retest interval based on an external measure, and to distinguish such changes from random response errors. METHODS: In our application, eighty participants completed the Symptoms of Illness Checklist (SIC) on two occasions, two weeks apart, immediately before interviews given on each occasion by one of two physicians in a crossover design. The physician interview scores served as external measures, and structural equation modeling was used to estimate the parameters of a model that corrected for the occasion-specific effect of participants' responses using information from the interviews. RESULTS: Correcting for changes in symptoms during the test-retest interval increased SIC test-retest reliability from .744 to .804 and significantly improved model fit (chi2(diff)(1) = 30.78, p < .001). CONCLUSIONS: The results suggest methods that can improve the evaluation of self-report health questionnaire test-retest reliability by identifying changes using an external measure, and distinguishing these from random response errors; these increased the estimated SIC test-retest reliability and indicated that the SIC was indeed able to measure changes over the studied time interval. This method can be applied across a broad range of questionnaires.

The Salient Stressor Impact Questionnaire (SSIQ): a measurement of the intensity and chronicity of stress.

High stress is known to affect health, but stress impact, determined by events and responses to them, has not been studied systematically. For the Salient Stressor Impact Questionnaire (SSIQ), the impact of events was assumed to depend on their salience and chronicity and the impact of responses on their chronicity and intensity with greater unfavorable appraisal associated with greater response. The SSIQ assessed a person's two most salient stressors. Chronicity items discriminated between clinically stressed and nonclinical participants and measured the chronicity of stressful feelings (distress) and the event. The remaining items measured the degree of distress and unfavorable appraisal. The SSIQ showed good test-retest and internal consistency reliability, concurrent validity, and stability across diverse populations. Exploratory analyses grouped items into distress, chronicity, and appraisal elements, and confirmatory analysis revealed a good fit to the hypothesized model. Preliminary data suggest that the SSIQ will be useful for studying relationships between stress and health.