Multiple Chemical Sensitivities Syndrome (MCS) remains a doubtful entity. Plaintiff counsel offering a medical expert who believes in the condition should expect a scientifically-based Defence challenge to its existence.
5 years ago 5 major criteria were proposed for a working diagnosis:
(1) symptoms are reproducible with exposure;
(2) condition is chronic;
(3) low levels of exposure result in manifestations of the syndrome;
(4) symptoms resolve with removal of incitants;
(5) responses occur to multiple, chemically unrelated substances. All the criteria resulted from self-report.
Multiple Chemical Sensitivities Syndrome is a condition diagnosed on self-report and without objective criteria
Scientific investigation has revealed no indicators of Allergy or abnormalities of the Immune System, indeed no objective clinical or pathological tests have hitherto identified sufferers from MCS.
The exceptions are psychological findings: current Anxiety or Depressive Disorder is significantly more common, and 25% of patients fulfilled criteria for Somatisation Disorder (Medical Litigation News Volume 2, Issue 2) before the onset of the chemical sensitivity. There has yet been insufficient rigorous research refuting or proving a psychological cause.
Although psychological cause is not proven, many MCS patients fulfil criteria for pre-existing or current psychiatric disorders
Researchers from the Mayo Clinic would like to substitute the term "Odor Aversion" to provide a better description of the frequently-disabling symptoms and to reverse the implied endorsement of a supposed Allergic or Immunological basis.
Early results of Behavioural Therapy support their proposition that some cases result from simple Pavlovian Conditioning.
"Absent the exposure..." will likely be difficult to prove
A recent Canadian study suggested that MCS might have a similar, if not identical, pathophysiological basis, to Panic Disorder.
In particular, the condition could be mimicked by an infusion of (alkaline) sodium lactate but not by a control solution of saline (salt water). Such production of the characteristic symptoms is peculiar to sufferers from the two conditions.
The majority of MCS patients tested also fulfilled the Diagnostic and Statistical Manual, 3rd Edition (DSM-III) criteria for Panic Disorder.
MCS would presently appear to result from a psychological vulnerability combined with a mistaken belief of toxic injury
According to this model, the symptoms would result from hyperventilation or overbreathing and should, therefore, be susceptible to the therapies effective in Panic Disorder.
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