Morriss, R K, Wearden, A J, Mullis, R · Journal of psychosomatic research · 1998 · DOI
This study tested whether the Chalder Fatigue Scale—a common questionnaire used to measure tiredness in ME/CFS patients—actually measures what it claims to measure. Researchers analyzed responses from 136 ME/CFS patients and found that fatigue has four distinct components: mental tiredness (linked to thinking problems), sleep difficulties, physical weakness (linked to low fitness), and depression. The results suggest the 11-item version of the scale works better than the original 14-item version for measuring fatigue in ME/CFS.
Understanding what the Chalder Fatigue Scale actually measures is crucial for ME/CFS research, as this instrument is widely used in clinical trials and patient assessments. This study provides evidence that the scale captures distinct dimensions of fatigue—cognitive, sleep-related, and physical—allowing researchers and clinicians to better interpret results and tailor assessments to individual patient experiences.
This study does not establish which factors cause the others—only that they co-occur and correlate with specific symptoms. As a cross-sectional analysis, it cannot determine whether fatigue leads to depression, depression causes fatigue, or they share a common biological cause. The findings also do not address how these fatigue dimensions change over time or respond to treatment.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
The first block is for the primary paper and is the citation you should use in research work. The atlas-snapshot line only applies if you are specifically referring to this atlas’s reading of the paper on the date shown.
Primary citation
Morriss, R K, Wearden, A J, & Mullis, R (1998). Exploring the validity of the Chalder Fatigue scale in chronic fatigue syndrome.. Journal of psychosomatic research. https://doi.org/10.1016/s0022-3999(98)00022-1
BibTeX
@article{mecfsatlas-morriss-1998-exploring-validity,
author = {Morriss, R K and Wearden, A J and Mullis, R},
title = {Exploring the validity of the Chalder Fatigue scale in chronic fatigue syndrome.},
journal = {Journal of psychosomatic research},
year = {1998},
doi = {10.1016/s0022-3999(98)00022-1},
note = {PubMed: 9835234},
url = {https://www.mecfsatlas.com/evidence/morriss-1998-exploring-validity},
}Atlas snapshot reference
ME/CFS Atlas. Generator v1 / Scanner v1.4 / policy v0.1. Accessed 2026-05-30. https://www.mecfsatlas.com/evidence/morriss-1998-exploring-validity
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