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This paper reviews the clinical and experimental literature on patients with multiple adverse responses to chemicals (Multiple Chemical Sensitivity Syndrome-MCS) and develops a model for MCS based on olfactory-limbic system dysfunction that overlaps in part with Post's kindling model for affective disorders. MCS encompasses a broad range of chronic polysymptomatic conditions and complaints whose triggers are reported to include low levels of common indoor and outdoor environmental chemicals, such as pesticides and solvents. Other investigators have found evidence of increased prevalence of depression, anxiety, and somatization disorders in MCS patients and have concluded that their psychiatric conditions account for the clinical picture. However, none of these studies has presented any data on the effects of chemicals on symptoms or on objective measures of nervous system function. Synthesis of the MCS literature with large bodies of research in neurotoxicology, occupational medicine, and biological psychiatry, suggests that the phenomenology of MCS patients overlaps that of affective spectrum disorders and that both involve dysfunction of the limbic pathways. Animal studies demonstrate that intermittent repeated low level environmental chemical exposures, including pesticides, cause limbic kindling. Kindling (full or partial) is one central nervous system mechanism that could amplify reactivity to low levels of inhaled and ingested chemicals and initiate persistent affective, cognitive, and somatic symptomatology in both occupational and nonoccupational settings. As in animal studies, inescapable and novel stressors could cross-sensitize with chemical exposures in some individuals to generate adverse responses on a neurochemical basis. The olfactory-limbic model raises testable neurobiological hypotheses that could increase understanding of the multifactorial etiology of MCS and of certain overlapping affective spectrum disorders.
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PMID:An olfactory-limbic model of multiple chemical sensitivity syndrome: possible relationships to kindling and affective spectrum disorders. 142 Jun 41

Multiple Chemical Sensitivity (MCS) is a clinical phenomenon in which individuals, after acute or intermittent exposure to one or more chemicals, commonly organophosphate pesticides (OPs), become overly sensitive to a wide variety of chemically-unrelated compounds, which can include ethanol, caffeine and other psychotropic drugs. The Flinders Sensitive Line (FSL) rats were selectively bred to be more sensitive to the OP diisopropylfluorophosphate (DFP) compared to their control counterparts, the Flinders Resistant Line (FRL) rats. The present paper will summarize evidence which indicates that the FSL rats exhibit certain similarities to individuals with MCS. In addition to their greater sensitivity to DFP, the FSL rats are more sensitive to nicotine and the muscarinic agonists arecoline and oxotremorine, suggesting that the number of cholinergic receptors may be increased, a conclusion now supported by biochemical evidence. The FSL rats have also been found to exhibit enhanced responses to a variety of other drugs, including the serotonin agonists m-chlorophenylpiperazine and 8-OH-DPAT, the dopamine antagonist raclopride, the benzodiazepine diazepam, and ethanol. MCS patients report enhanced responses to many of these drugs, indicating some parallels between FSL rats and MCS patients. The FSL rats also exhibit reduced activity and appetite and increased REM sleep relative to their FRL controls. Because these behavioral features and the enhanced cholinergic responses are also observed in human depressives, the FSL rats have been proposed as a genetic animal model of depression. It has also been reported that MCS patients have a greater incidence of depression, both before and after onset of their chemical sensitivities, so cholinergic supersensitivity may be a state predisposing individuals to depressive disorders and/or MCS. Further exploration of the commonalities and differences between MCS patients, human depressives, and FSL rats will help to elucidate the mechanisms underlying MCS and could lead to diagnostic approaches and treatments beneficial to MCS patients.
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PMID:Potential animal model of multiple chemical sensitivity with cholinergic supersensitivity. 871 28

Toxicology has two goals. The first is to identify and characterize the adverse effects that can be produced in biological systems by exposure to chemicals and the second is to use this information to predict the type and severity of responses in other species and exposure situations. The tools that the toxicologist uses to detect and describe the adverse effects of chemical exposure include the traditional acute, subchronic, and chronic studies in animals plus a variety of special studies designed to demonstrate specific organ damage, reproductive and teratogenic effects, neurotoxicity, immunotoxicity, genotoxicity, and other responses. These are often supplemented with studies of the kinetics and the mechanism of action and more recently with studies designed to elucidate the molecular basis for cancer and other effects. Theses studies together with the information on exposure provide the basis for subsequent toxicologic predictions. Although general effects such as weight loss and mortality are included in toxicity protocols, most of the toxicology tests are related to specific end-organ toxicity or to mechanism or behavioral studies. We do not have animal protocols to study individually the subjective symptoms described for multiple chemical sensitivity, such as depression, fatigue, headache, and memory loss, and our tests lack sufficient specificity to evaluate a syndrome which is composed primarily of such symptoms. Since all chemicals can produce adverse effects under some conditions of exposure, toxicologic predictions are most useful when they specify both the type of adverse effect anticipated and the dose required to produce the effect. Multiple chemical sensitivity does not appear to consistently involve specific chemicals or specific adverse effects and the effects observed are reported to lack evidence of a threshold and to occur at extremely low levels. It is difficult to include these parameters in any reasonable toxicologic prediction relating cause and response in multiple chemical sensitivity or similar conditions.
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PMID:Specificity and dosimetry of toxicologic responses. 892 57

Multiple chemical sensitivity (MCS) could be called a phenomenon rather than an illness. No single widely accepted test of physiological function can be shown to correlate with the symptoms presented by the patients. In addition to allergy and asthma, patient history can include various "illnesses", and the "diagnosis" is often made by the patient, usually alone or with the help of clinical ecologists. This paper reports the experiences from a department of occupational medicine. More than 80% of the patients were women and solvent exposure was the most common cause of chemical intolerance reported by the patients. Many patients also reported psychosocial stressors. The patients also showed mood disorders with irritability, anxiety, sleep disturbances and depression, often with thoughts centered around different organ symptoms. The symptomatology of MCS is still nonspecific and in no way diagnostic of a specific illness or a medically acceptable syndrome. It may indicate many other conditions, both organic disease and psychopathology.
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PMID:Clinical features of multiple chemical sensitivity. 945 70

Multiple chemical sensitivity (MCS) is a syndrome in which multiple symptoms reportedly occur with low-level chemical exposure. Several theories have been advanced to explain the cause of MCS, including allergy, toxic effects and neurobiologic sensitization. There is insufficient scientific evidence to confirm a relationship between any of these possible causes and symptoms. Patients with MCS have high rates of depression, anxiety and somatoform disorders, but it is unclear if a causal relationship or merely an association exists between MCS and psychiatric problems. Physicians should compassionately evaluate and care for patients who have this distressing condition, while avoiding the use of unproven, expensive or potentially harmful tests and treatments. The first goal of management is to establish an effective physician-patient relationship. The patient's efforts to return to work and to a normal social life should be encouraged and supported.
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PMID:Multiple chemical sensitivity syndrome. 1022 Dec 99

When abnormal psychologic/psychiatric symptom data are obtained on personality tests or psychiatric interviews administered to patients who report symptoms of Multiple Chemical Sensitivities Syndrome, investigators typically attribute these to either psychiatric traits or to psychogenic origins of illness. The primary purpose of these studies was the evaluation of the plausibility of nonpsychiatric explanations of psychologic/psychiatric symptom data. In Study 1, patients with Multiple Chemical Sensitivities Syndrome used the Minnesota Multiphasic Personality Inventory 2 (MMPI-2) to describe which items had changed after they developed the condition. In Study 2, three diverse groups of professionals predicted which items on the MMPI-2 might change after a mentally healthy person developed the Syndrome or a condition resembling it. In Study 3, a second sample of Multiple Chemical Sensitivities Syndrome patients completed the MMPI-2 and other questionnaires by mail, which allowed the authors to ascertain whether these patients showed more or different psychopathology than was described by patients and hypothesized by professionals. Data from Study 1 patient informants indicated that developing the syndrome might result in a psychopathological MMPI-2 profile, characterized by abnormal Hypochondriasis and Hysteria scale scores. Professionals in Study 2 showed a consensus about hypothesized MMPI-2 changes following the development of the syndrome. These changes likely elevated the Hypochondriasis, Hysteria, Psychasthenia, Depression, and Schizophrenia scale scores. In Study 3, the patients taking the MMPI-2 showed elevations on the Hypochondriasis, Hysteria, Depression (women only), and Schizophrenia scales. Abnormal scores were associated closely with greater severity of illness and greater adjustment to illness. The strategy of administering psychometric tests to ill populations for the purposes of evaluating psychiatric illness or traits, and/or psychogenic origins of illness was shown to be potentially misleading.
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PMID:Psychiatric inferences from data on psychologic/psychiatric symptoms in multiple chemical sensitivities syndrome. 1090 99

Patients with sensitivities to multiple chemicals report symptoms of cognitive dysfunction, respiratory distress, and mood disturbance. Lifetime and current psychiatric disorders, personality traits associated with symptom reporting, and tests of cognitive function were compared between 30 subjects with Multiple Chemical Sensitivities (MCS), 19 asthmatics, and 31 healthy controls. Relative to asthmatics and controls, more MCS subjects met criteria for current depression and somatization disorder. MCS subjects and asthmatics scored significantly higher than controls on scales of chemical odor intolerance and anxiety sensitivity, both of which were significant predictors of physical symptoms. Few differences on objective neuropsychological tests were noted. However, MCS subjects with comorbid depression performed significantly worse on a verbal memory test relative to asthmatics but not to controls. Anxiety and depression are significant contributors to the physical and cognitive symptoms of MCS subjects.
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PMID:Anxiety sensitivity and depression in multiple chemical sensitivities and asthma. 1239 67

Multiple chemical sensitivity (MCS) is a syndrome in which multiple symptoms occur with low-level chemical exposure; whether it is an organic disease initiated by environmental exposure or a psychological disorder is still controversial. We report a 38-year-old male worker with chronic toluene exposure who developed symptoms such as palpitation, insomnia, dizziness with headache, memory impairment, euphoria while working, and depression during the weekend. Upon cessation of exposure, follow-up neurobehavioural tests, including the cognitive ability screening instrument and the mini-mental state examination, gradually improved and eventually became normal. Although no further toluene exposure was noted, non-specific symptoms reappeared whenever the subject smelled automotive exhaust fumes or paint, or visited a petrol station, followed by anxiety with sleep disturbance. During hospitalization for a toluene provocation test, there was no difference between pre-challenge and post-challenge PaCO(2), PaO(2), SaO(2) or pulmonary function tests, except some elevation of pulse rate. The clinical manifestations suggested that MCS was more relevant to psychophysiological than pathophysiological factors.
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PMID:Central neurological abnormalities and multiple chemical sensitivity caused by chronic toluene exposure. 1458 47

Idiopathic Environmental Intolerance (IEI) has been associated with psychogenic factors and an increased number of comorbid psychiatric disorders such as depression and anxiety disorder. The purpose of the current study was to examine a possible overlap of psychological and somatic symptoms between subjects with IEI and patients with major depression and schizophrenia as well as to specify characteristic differences. The different symptom clusters included symptoms of chemical intolerance, neurotoxicity and psychological distress as well as measurements of mental health such as anxiety, depression, somatoform symptoms, and schizophrenia-specific disturbances in cognitive domains. IEI patients reported higher overall levels in physical symptoms such as chemical intolerance, neurotoxicity and somatic symptoms not attributable to an organic cause. Schizophrenia patients showed higher overall levels in self-experienced disturbances in several schizophrenia-specific cognitive domains, whereas general psychological distress, anxiety and depression were rated highest by patients with major depression. Importantly, the groups markedly differed in the shapes of profiles of various symptom clusters. Our results provide evidence that IEI patients can be distinguished on the phenomenological level from patients with major depression or schizophrenia, and that distinct domains of psychological and somatic symptoms are particularly problematic in specific diagnostic groups.
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PMID:Differences in psychological and somatic symptom cluster score profiles between subjects with Idiopathic environmental intolerance, major depression and schizophrenia. 2811 22

Background Multiple chemical sensitivity (MCS) is a chronic, disabling condition characterized by recurrent multisystem symptoms triggered by common airborne chemicals. Evidence points towards abnormal sensory processing in the central nervous system (CNS) as a likely pathophysiological mechanism. No effective treatment has yet been reported, but clinical observations suggest that as pulsed electromagnetic fields (PEMF) is a treatment for some CNS disorders (depression and chronic pain), it may also be a treatment modality for MCS. Methods In an open case study, the effects of PEMF were assessed in three MCS patients. All cases received 30 min daily treatment 5 days a week for 8 consecutive weeks. Symptoms and functional impairments related to MCS, depressive symptoms, and capsaicin-induced secondary punctate hyperalgesia were assessed at baseline and weekly until an 18-week follow-up. Results Two of the three cases showed considerable improvement on all measures of symptoms and functional impairments related to MCS in response to PEMF therapy. One case showed no improvement and during the treatment period was unexpectedly diagnosed with depression. Conclusion Our findings indicate potential benefits of PEMF therapy in MCS. Implication The therapeutic effect of PEMF in MCS needs to be investigated by a randomized placebo-controlled trial.
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PMID:Two of three patients with multiple chemical sensitivity had less symptoms and secondary hyperalgesia after transcranially applied pulsed electromagnetic fields. 2991 74


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