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1Department of Clinical Psychology, University of Groningen, The Netherlands. w.arrindell@ppsw.rug.nl
Behaviour Research and Therapy
|October 3, 2001
Summary
Repeatedly assessing psychiatric patients without intervention often shows reduced symptoms, a re-test effect. This finding impacts longitudinal study validity and requires careful consideration in research.
Area of Science:
- Psychiatry
- Psychological assessment
- Clinical research methodology
Background:
- Repeated assessments in psychiatric research, without intervention, can yield score changes.
- This re-test effect is a potential threat to the validity of longitudinal studies.
- The phenomenon has received insufficient attention from researchers.
Purpose of the Study:
- To investigate the re-test effect in psychiatric patients.
- To examine the impact of repeated testing on state and trait measures.
- To assess the prevalence and magnitude of re-test effects in clinical samples.
Main Methods:
- Two independent clinical samples were assessed.
- The Symptom Check List-90-Revised (SCL-90-R) and other state/trait measures were used.
- Assessments were conducted at intake and after a time interval (mean 93 days, range 11-350 days).
Main Results:
- A re-test effect was observed for most measures administered.
- In cases with significant testing effects, 54-72% of patients showed lower scores at re-test.
- This indicates a trend towards reduced psychopathology scores upon repeated measurement.
Conclusions:
- The re-test effect is a significant factor in psychiatric research with repeated measures.
- Findings have practical and scientific implications for interpreting longitudinal data.
- Eleven hypotheses, including associative processing and self-monitoring, are proposed to explain the re-test effect.