E2 ModerateModerate confidencePEM not requiredCross-SectionalPeer-reviewedReviewed
Standard · 3 min
A controlled comparison of multiple chemical sensitivities and chronic fatigue syndrome.
Fiedler, N, Kipen, H M, DeLuca, J et al. · Psychosomatic medicine · 1996 · DOI
Quick Summary
This study compared people with multiple chemical sensitivities (MCS), chemical sensitivities without a clear trigger (CS), and chronic fatigue syndrome (CFS) to healthy controls. Researchers found that chemically sensitive patients reported more lifestyle disruption and avoided more substances than CFS patients, but all three patient groups had higher rates of psychiatric conditions and unexplained physical symptoms compared to healthy people. Interestingly, standard memory and thinking tests did not show significant differences between groups, suggesting that cognitive problems in these conditions may not show up on typical office-based tests.
Why It Matters
This study provides evidence that ME/CFS, while associated with elevated psychiatric symptoms, is not primarily a psychiatric disorder—most CFS patients (61%) did not meet psychiatric diagnostic criteria. The findings suggest that the neuropsychological impairments patients report may require specialized testing conditions rather than standard office-based assessments, supporting the biological basis of these illnesses.
Observed Findings
MCS and CS patients reported significantly more lifestyle changes and identified more chemical substances that made them ill compared to CFS and control groups.
74% of MCS and 61% of CFS patients did not qualify for any current Axis I psychiatric diagnosis, while 69% of CS patients met psychiatric diagnostic criteria.
44% of MCS, 42% of CS, and 53% of CFS patients showed clinically significant MMPI-2 elevations on somatoform disorder scales, compared to 0% of controls.
No significant neuropsychological differences were detected between groups on standardized testing, with one exception: a complex visual memory test.
All three patient groups reported significantly more physical symptoms with no medical explanation compared to normal controls.
Inferred Conclusions
Chemical sensitivities (MCS and CS) are distinct from CFS, characterized primarily by avoidance of specific substances rather than generalized fatigue.
Psychiatric symptoms are elevated in CFS but do not define the condition, as most CFS patients lack psychiatric diagnoses.
Standardized neuropsychological testing may be insufficient to detect cognitive impairments in these populations; specialized testing under controlled exposure conditions may be necessary.
Remaining Questions
Why do standard neuropsychological tests fail to detect cognitive deficits that patients report experiencing in daily life?
What This Study Does Not Prove
This study does not prove that chemical sensitivities or CFS are caused by psychiatric conditions; the majority of patients with these conditions did not meet psychiatric diagnoses. Cross-sectional design cannot determine whether psychiatric symptoms arose before, after, or independently of CFS onset. The study also cannot explain why standard cognitive tests failed to detect reported cognitive deficits, leaving open the question of whether impairments require specific provocation conditions.
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 →
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Do psychiatric symptoms in these patient groups represent comorbid conditions, consequences of chronic illness, or features of the underlying pathophysiology?
What specific exposure conditions would reveal neuropsychological deficits not apparent on standard testing?
What mechanisms explain the higher rates of psychiatric diagnoses in CS (69%) compared to MCS (26%) and CFS (39%)?