Neuroanatomy and Neurochemical Mechanisms of Time-Dependent Sensitization

Time-dependent sensitization (TDS) is a phenomenon described in rodents as an enhancement in the behavioral and neurochemical responses to intermittent exposure to psychostimulant drugs. Time-dependent sensitization also occurs after repeated encounters with environmental stress. Several features of TDS parallel those of multiple chemical sensitivity (MCS) in humans, and these similarities have led to the hypothesis that MCS may be explained in part by a similar sensitization process that occurs in rodents. In the studies presented here, we discuss some of the critical features of TDS following repeated exposure to cocaine and environmental stress, including the anatomical and neurochemical pathways utilized in expressing TDS. In addition, we discuss the possible neurochemical basis for individual differences in responsiveness to stimuli, including novelty and cocaine. The striking similarities between TDS and MCS suggest it may be possible to develop an animal model of MCS, using TDS in rodents as its basis.

Psychological Bases of Symptom Reporting: Perceptual and Emotional Aspects of Chemical Sensitivity

The reporting of physical symptoms is influenced to a large degree by psychological processes. Individuals are more likely to notice subtle sensations in environments lacking in stimulation than those demanding external attention. The beliefs or schemas that people hold dictate where and how they attend to their bodies as well. These normal perceptual processes help explain why people are of ten poor at accurately detecting internal physiological activity. Several individual differences are also related to the symptom reporting process. Females are more likely to base their symptom reports on external situational cues than are males. In addition, individuals with chronic anxiety those high in Negative Affectivity (NA) report more symptoms than those low in NA. Finally, individuals who have had traumatic experiences, either in childhood or within 16 months prior to a major symptom reporting episode, tend to be high symptom reporters. Several recommendations are made to help researchers and clinicians distinguish between psychological or perceptual factors with presumed biological effects. One implication of this work is that MCS and allied syndromes should be viewed as both a mental and a physical health problem.

Noise sensitivity and hyperacusis in patients affected by multiple chemical sensitivity

PURPOSE

The aim of this study was to investigate the presence of noise sensitivity and hyperacusis in patients suffering from multiple chemical sensitivity (MCS), a chronic condition characterized by several symptoms following low-level chemical exposure. Moreover, distortion product otoacoustic emissions (DPOAE) were performed to further study cochlear function.

METHODS

A questionnaire-based survey was performed. Eighteen MCS patients, selected with strict diagnostic criteria, and 20 healthy age- and gender-matched subjects filled Weinstein's Noise Sensitivity Questionnaire (WNS) and Khalfa's Hyperacusis Questionnaire (HQ). Results were compared with scores from the quick Environmental Exposure Sensitivity Index (qEESI), a routinarily used questionnaire to screen MCS symptoms, and with DPOAE values. An analysis of variance (ANOVA) was performed between MCS and control subjects scores; moreover, Spearman's rank correlation test was performed between questionnaire results.

RESULTS

ANOVA testing on DPOAE values showed any significant difference between groups, while WNS, HQ and qEESI scores were significantly higher in MCS group compared to controls. Correlation analysis showed strong positive correlation between WNS, HQ and qEESI in MCS subjects.

CONCLUSIONS

For the first time, auditory-related perceptual disorders were studied in MCS. A strong association between WNS, HQ results and MCS symptoms severity has been highlighted. These findings suggest that decreased sound tolerance and noise sensitivity could be considered as possible new aspects of this syndrome, contributing to its peculiar phenotype. Furthermore, as DPOAE values did not differ from healthy subjects, present findings might suggest a 'central' source for such disorders in this group of patients.

The correlation between mental health and multiple chemical sensitivity: a survey study in Japanese workers

OBJECTIVE

This study was designed to determine the correlation between mental health and multiple chemical sensitivity (MCS).

METHOD

The present study was conducted at two companies in 2011; both in Kyushu, Japan. The "subjective symptoms" subscale of the "Self-diagnosis Checklist for Assessment of Workers' Accumulated Fatigue" was used as a mental health subscale. To determine if multiple chemical exposure has an impact on mental health, we composed an original path model using structural equation analysis.

RESULT

Our final path model can be regarded as good: CMIN/DF = 1.832, CFI = 0.996, and RMSEA = 0.038, AIC = 71.158. As expected, chemical sensitivity and other chemical sensitivity scores predicted the health effects of multiple chemical exposure (β = 0.19, 0.64). Mental health was predicted by symptom severity and life impact (β = 0.56 and 0.12), which were both affected by multiple chemical exposure (β = 0.38 and 0.89, respectively).

CONCLUSION

As far as we are aware, this is the first study using path analysis to explore whether MCS can indicate mental health in worker populations worldwide, and we found a significant causal relationship between them. This could indicate that more focus should be placed on the impact of MCS on mental health in future investigations.

Brain sensitization to external and internal stimuli

Sensitization is defined as a non-associative learning process occurring when repeated administrations of a stimulus result in a progressive amplification of a response (Shettleworth, 2010). The purpose of this review paper is to discuss whether brain sensitization is helpful in common health problems in man. The paper reviews data on brain sensitization covering increased behavioral, physiological, cognitive, and emotional responses in man and animals. The paper concludes that brain sensitization may be a helpful concept to understand subjective and "unexplained" health complaints (nonspecific muscle pain, mood changes, fatigue, and gastrointestinal complaints), and, therefore, relevant for evidence based treatment and prevention of these common health problems.

Emotion: The Self-regulatory Sense

While emotion is a central component of human health and well-being, traditional approaches to understanding its biological function have been wanting. A dynamic systems model, however, broadly redefines and recasts emotion as a primary sensory system-perhaps the first sensory system to have emerged, serving the ancient autopoietic function of "self-regulation." Drawing upon molecular biology and revelations from the field of epigenetics, the model suggests that human emotional perceptions provide an ongoing stream of "self-relevant" sensory information concerning optimally adaptive states between the organism and its immediate environment, along with coupled behavioral corrections that honor a universal self-regulatory logic, one still encoded within cellular signaling and immune functions. Exemplified by the fundamental molecular circuitry of sensorimotor control in the E coli bacterium, the model suggests that the hedonic (affective) categories emerge directly from positive and negative feedback processes, their good/bad binary appraisals relating to dual self-regulatory behavioral regimes-evolutionary purposes, through which organisms actively participate in natural selection, and through which humans can interpret optimal or deficit states of balanced being and becoming. The self-regulatory sensory paradigm transcends anthropomorphism, unites divergent theoretical perspectives and isolated bodies of literature, while challenging time-honored assumptions. While suppressive regulatory strategies abound, it suggests that emotions are better understood as regulating us, providing a service crucial to all semantic language, learning systems, evaluative decision-making, and fundamental to optimal physical, mental, and social health.

Allergological and toxicological aspects in a multiple chemical sensitivity cohort

Background. Multiple chemical sensitivity (MCS) is a chronic condition characterized by an exaggerated response to toxicants. We ascertained the prevalence of allergy to metals and toxicological aspects in MCS patients. Methods. We conducted a retrospective review of medical records of 41 patients with MCS. We performed patch testing (n = 21) for dental series and did lymphocyte transformation test (n = 18) for metals. We measured mercury in samples of blood (n = 19), urine (n = 19), saliva (n = 20), and scalp hair (n = 17) to investigate the association between mercury levels and cases of MCS. Results. The prevalence of metal immune hypersensitivity in a subset of 26 patients was 92.3 percent. Elevations of mercury occurred in 81.2 percent (26 of 32). The mean (±SD) in blood concentrations of mercury was 7.6 ± 13.6 μg/L; mean in urine was 1.9 ± 2.5 μg/L; mean in scalp hair was 2.2 ± 2.5 μg/g; mean in saliva was 38.1 ± 52.1 μg/L. Subgroup analyses showed that elevation of mercury levels in biological matrices were associated with mercury amalgams in patients with MCS (22 patients), compared with controls (8 patients) (odds ratio 11 : 95 percent confidence interval 1.5 to 81.6; P = 0.023). Conclusions. Our data show an increased prevalence of metal allergy and elevation of mercury levels in bioindicators among patients with MCS.

The neuroprogressive nature of major depressive disorder: pathways to disease evolution and resistance, and therapeutic implications

In some patients with major depressive disorder (MDD), individual illness characteristics appear consistent with those of a neuroprogressive illness. Features of neuroprogression include poorer symptomatic, treatment and functional outcomes in patients with earlier disease onset and increased number and length of depressive episodes. In such patients, longer and more frequent depressive episodes appear to increase vulnerability for further episodes, precipitating an accelerating and progressive illness course leading to functional decline. Evidence from clinical, biochemical and neuroimaging studies appear to support this model and are informing novel therapeutic approaches. This paper reviews current knowledge of the neuroprogressive processes that may occur in MDD, including structural brain consequences and potential molecular mechanisms including the role of neurotransmitter systems, inflammatory, oxidative and nitrosative stress pathways, neurotrophins and regulation of neurogenesis, cortisol and the hypothalamic-pituitary-adrenal axis modulation, mitochondrial dysfunction and epigenetic and dietary influences. Evidence-based novel treatments informed by this knowledge are discussed.

Genetic Component of Noise Sensitivity

We investigated the genetic component of noise sensitivity using a twin-study design. The study sample consisted of 573 same-sexed twin pairs from the Finnish Twin Cohort. The 131 monozygotic (MZ) and 442 dizygotic (DZ) twin pairs with an age range of 31 to 88 years replied to a questionnaire on noise and health-related items in 1988. The noise sensitivity of respondents was defined as high, quite high, quite low or low. MZ pairs were more similar with regards noise sensitivity than DZ pairs, and quantitative genetic modeling indicated significant familiality. The best z-fitting genetic model provided an estimate of heritability of 36% (95% CI = .20–.50) and when hearing impaired subjects were excluded this rose to 40% (95% CI = .24–.54). In conclusion, noise sensitivity does aggregate in families and probably has a genetic component.

Activation of cell-mediated immunity in depression: association with inflammation, melancholia, clinical staging and the fatigue and somatic symptom cluster of depression

BACKGROUND

Depression is characterized by activation of cell-mediated immunity (CMI), including increased neopterin levels, and increased pro-inflammatory cytokines (PICs), such as interleukin-1 (IL-1) and tumor necrosis factor-α (TNFα). These PICs may induce depressive, melancholic and chronic fatigue (CF) symptoms.

METHODS

We examined serum neopterin and plasma PIC levels in depressive subgroups in relation to the depressive subtypes and the melancholic and CF symptoms of depression. Participants were 85 patients with depression and in 26 normal controls. Severity of depression was assessed with the Hamilton Depression Rating Scale (HDRS) and severity of CF with the Fibromyalgia and Chronic Fatigue Syndrome (FF) Rating Scale.

RESULTS

Serum neopterin was significantly higher in depressed patients and in particular in those with melancholia. There were positive correlations between serum neopterin, the plasma PICs and the number of previous depressive episodes. Neopterin and TNFα were associated with melancholia, while both PICs were associated with CF. Melancholia-group membership was predicted by the HDRS and neopterin, and CF group membership by age, the FF score and serum TNFα.

DISCUSSION

Depression and melancholia are accompanied by CMI activation, suggesting that neopterin plays a role in their pathophysiology, e.g. through activation of oxidative and nitrosative stress and apoptosis pathways. The intertwined CMI and inflammatory responses are potentially associated with the onset of depression and with the melancholic and CF symptoms of depression. Exposure to previous depressive episodes may magnify the size of CMI and PIC responses, possibly increasing the likelihood of new depressive episodes. CMI activation and inflammation may contribute to the staging or recurrence of depression.

Idiopathic environmental intolerance: Part 1: A causation analysis applying Bradford Hill's criteria to the toxicogenic theory

Idiopathic environmental intolerance (IEI) is a descriptor for a phenomenon that has many names including environmental illness, multiple chemical sensitivity and chemical intolerance. Toxicogenic and psychogenic theories have been proposed to explain IEI. This paper presents a causality analysis of the toxicogenic theory using Bradford Hill's nine criteria (strength, consistency, specificity, temporality, biological gradient, biological plausibility, coherence, experimental intervention and analogy) and an additional criteria (reversibility) and reviews critically the scientific literature on the topic. The results of this analysis indicate that the toxicogenic theory fails all of these criteria. There is no convincing evidence to support the fundamental postulate that IEI has a toxic aetiology; the hypothesised biological processes and mechanisms are implausible.

Elucidating the unexplained underperformance syndrome in endurance athletes : the interleukin-6 hypothesis

The unexplained underperformance syndrome (UPS), previously known as the overtraining syndrome (OTS), has been defined as a persistent decrement in athletic performance capacity despite 2 weeks of relative rest. It has been proposed that UPS may be caused by excessive cytokine release during and following exercise causing a chronic inflammatory state and 'cytokine sickness'. This article extends that hypothesis by proposing that time-dependent sensitisation could provide a model through which the aetiology of UPS may be explained. In this model, the principal abnormal factors in UPS are an increased production of and/or intolerance to interleukin (IL)-6 during exercise. Strategies to attenuate the IL-6 response to exercise that may also reduce an athlete's susceptibility to UPS are proposed.

Multiple chemical sensitivity and idiopathic environmental intolerance (part one)

Multiple chemical sensitivity/idiopathic environmental intolerance (MCS/IEI) is a commonly used diagnostic term for a group of symptoms. These symptoms have been described and commented on for more than 15 years in the USA. Recently, it has also been observed in Japan. The main features of this syndrome are multiple symptoms involving in multiple organ systems that are precipitated by a variety of chemical substances with relapses and exacerbation under certain conditions when exposed to very low levels which do not affect the population at large. There are no laboratory markers or specific investigative findings. Although traditional medical organizations have not agreed on a definition for this syndrome due to the lack of obvious evidence to demonstrate the existence of these symptoms, it is being increasingly recognized. It constitutes an increasing percentage of the caseload at occupational/environmental medical clinics.Part one of this review article discusses pathophysiological theories, substances which cause symptoms, prevalence in the general and specific populations, past history and family history, and clinical symptoms of MCS/IEI patients.

Idiopathic Environmental Intolerance

Toxicogenic and psychogenic theories have been proposed to explain idiopathic environmental intolerance (IEI). Part 2 of this article is an evidence-based causality analysis of the psychogenic theory using an extended version of Bradford Hill's criteria. The psychogenic theory meets all of the criteria directly or indirectly and is characterised by a progressive research programme including double-blind, placebo-controlled provocation challenge studies. We conclude that IEI is a belief characterised by an overvalued idea of toxic attribution of symptoms and disability, fulfilling criteria for a somatoform disorder and a functional somatic syndrome. A neurobiological diathesis similar to anxiety, specifically panic disorder, is a neurobiologically plausible mechanism to explain triggered reactions to ambient doses of environmental agents, real or perceived. In addition, there is a cognitively mediated fear response mechanism characterised by vigilance for perceived exposures and bodily sensations that are subsequently amplified in the process of learned sensitivity. Implications for the assessment and treatment of patients are presented.

Sensitization and subjective health complaints

Why is it that some of us have more pain, more fatigue, and more gastrointestinal trouble than others? Is it possible that there are brain mechanisms and psychological mechanisms that make some people sensitized to specific complaints? In this concluding paper we review the historical and theoretical background, discuss the evidence and theoretical positions in the contributions, and draw some conclusions. Traditional psychosomatic models had less predictive value and less therapeutic importance than what was hoped for. The main problem with these models was the lack of a pathophysiological explanation for why psychological problems could be related to somatic disease. Sustained arousal or "allostatic load" offers more plausible and acceptable mechanisms for pathology, and, to some extent, for sensitization and illness. The combination of cognitive psychology and neurophysiology offers a model for somatic pathology, and, perhaps more important, also for the understanding of subjective complaints and illness.

Sensitization as a mechanism for multiple chemical sensitivity: relationship to evolutionary theory

Multiple chemical sensitivity (MCS) is a disorder in humans attributed to prior chemical exposure. Sensitization is an amplification of neuronal responsiveness that elicits increased behavioral responding to stimuli, and occurs in a recently developed rat model of MCS. Rats were exposed to repeated formaldehyde (Form) and their response in three behavioral tests, including locomotor activity after a cocaine challenge, conditioned fear, and behavioral avoidance of Form, was assessed. In all three tests, rats demonstrated sensitized behaviors, implicating amplified responding within specific limbic brain regions. Evolutionary theory in the context of MCS specifies how the behavioral strategies of those with MCS are consistent with the notion that their self-perceived sense of survival and reproductive fitness may be threatened by chemical exposures. This behavior may be mediated by the same limbic brain regions that become sensitized after repeated chemical exposure in animals.

Idiopathic environmental intolerances (formerly multiple chemical sensitivity) psychiatric perspectives

Idiopathic environmental intolerances (IEI)/multiple chemical sensitivity (MCS) is characterized by various somatic symptoms which cannot be explained organically, but are attributed to the influences of toxic environmental chemicals in low, usually harmless doses. In the absence of a widely accepted definition of IEI, contradictory aetiological hypotheses and therapeutic suggestions are discussed. Some authors doubt the existence of IEI/MCS as a disease entity of its own. The label IEI does not implicate neither a diagnosis of somatic disease nor that it is caused by an avoidable exposure. Many IEI patients suffer from psychiatric diseases. A majority of them can be diagnosed as somatoform disorders. Consequently, psychiatric therapies could be effective. This review describes the current knowledge about IEI/MCS, outlines a diagnostic algorithm and a psychotherapeutic concept for variants of IEI understood as a somatoform disorder.

A multiple center study of multiple chemical sensitivity syndrome

The lack of widely accepted, standardized, clinical and epidemiologic criteria for Multiple Chemical Sensitivity syndrome has led to confusion about the identification of the condition and has slowed pertinent research. In this article, the authors evaluated the psychometric properties of 2 sets of clinical/epidemiologic criteria for Multiple Chemical Sensitivity syndrome. In this cross-sectional survey of 1,166 patients who visited outpatient occupational, otolaryngology, allergy, and clinical ecological clinics, the authors used the aforementioned sets of criteria to (a) estimate the prevalence of the syndrome in these varied samples and (b) compare the current diagnostic practices of traditional physician specialists with those of clinical ecologists. The authors used a patient-completed questionnaire to assess the medical, psychosocial, and psychological status of patients who reported multiple chemical sensitivities. This approach enabled the formulation of 6 domains, which represented commonly observed characteristics of the syndrome. The authors used a physician-completed questionnaire to collect diagnoses of Multiple Chemical Sensitivity syndrome and other medical conditions. Domains, which were operationalized by the questionnaire and comprised the 2 sets of criteria for identification of the Multiple Chemical Sensitivity syndrome, had test-retest reliabilities that exceeded .75 and estimates of internal consistency that ranged between .59 and .94. Evidence of construct and face validity was considered acceptable. The overall clinic-based prevalences of Multiple Chemical Sensitivity syndrome, based on 6 and 4 domains, were 7% and 23%, respectively. Regardless of the identifying set of criteria used, physicians' diagnoses had relatively low sensitivities (range = 6-50%) and relatively high specificities (range = 82-99%). The study data suggested that the domains operationalized by the questionnaire had reasonable psychometric characteristics. Study data also support the fact that Multiple Chemical Sensitivity syndrome is often overlooked--even by those physicians who treat it most frequently--and that use of both sets of objective criteria for identifying the syndrome would greatly improve the sensitivity of physician diagnoses.

Sensitization, subjective health complaints, and sustained arousal

The purpose of this presentation is to discuss the possibility that sensitization is a psychobiological mechanism underlying not only multiple chemical sensitivity (MCS), but a much more general cluster of illness, referred to as "subjective health complaints". Sustained arousal, or sustained "stress" responses, may be an important factor for the development of these conditions. Patients with subjective complaints without objective changes are sometimes referred to as having "fashionable diagnoses" or "unexplained symptoms". They may be given diagnoses like MCS, epidemic fatigue, chronic fatigue syndrome, burnout, stress, a variety of intoxications, environmental illness, radiation, multiple chemical hypersensitivity, food intolerance, functional dyspepsia, irritable bowel, myalgic encephalitis, postviral syndrome, yuppie flu, fibromyalgia, or vital exhaustion. One issue is whether this is one general condition or separate entities. Another issue is whether sensitization may be the psychobiological mechanism for most or all of these conditions. Finally, is it likely that sustained arousal may facilitate the development of sensitization in some or many neural circuits? In this review, the main emphasis will be on musculoskeletal pain. This is the most frequent and most expensive condition for sickness compensation and disability. The comorbidity of other complaints, however, will also be taken into account.

The inflammatory response following delivery is amplified in women who previously suffered from major depression, suggesting that major depression is accompanied by a sensitization of the inflammatory response system

BACKGROUND

There is now evidence that some patients with major depression show an activation of the inflammatory response system (IRS). This study was carried out to examine whether major depression may induce sensitization with increased IRS responses to the stress of child birth.

METHODS

Serum concentrations of interleukin-6 (IL-6), the soluble IL-6 receptor (sIL-6R), sgp130 (the IL-6 signal transducing protein) and the sIL-1R antagonist (sIL-1RA) were determined in 16 and 50 women with and without a lifetime history of major depression, respectively. Blood was collected 3-6 days before delivery and 1 and 3 days after delivery. On each occasion the women completed the Zung Depression Rating Scale (ZDS).

RESULTS

Serum IL-6, sIL-6R, sIL-1RA were significantly higher 1 and 3 days after delivery than before. Women who had suffered from a lifetime history of major depression had greater increases in serum IL-6 and sIL-1RA in the early puerperium than women without a lifetime history. Women who had suffered from a lifetime history of major depression had significantly higher IL-6, and sIL-1RA concentrations 1 and 3 days after delivery than women with a negative life-time history.

CONCLUSIONS

The responses of IL-6 and sIL-1RA following delivery are amplified in women who previously suffered from major depression. The results suggest that major depression is accompanied by a sensitization of the IRS.

Environmental sensitivities: prevalence of major symptoms in a referral center: the Nova Scotia Environmental Sensitivities Research Center Study

Although the phenomenon of environmental sensitivities (ES) has no clear etiology nor well-accepted pathophysiology, affected individuals experience symptoms that cause varying levels of dysfunction. Through a dedicated, government-funded research and treatment center, a detailed questionnaire covering 217 symptoms in 13 systems was mailed in 1997-1998 to 812 individuals referred to the center by physicians. A total of 385 (47%) questionnaires were returned, and data were analyzed on 351 individuals. Participants tended to be women (80%), middle-aged individuals (37% age 40-49 years), and those in higher educational groups (28% completed university), but there was wide variation in demographic variables. General symptoms such as difficulty concentrating, fatigue, forgetfulness, and irritability dominated the overall prevalence of symptoms since the start of their illness. Those related to irritation such as sneezing, itchy or burning eyes, and hoarseness or loss of voice were more common after exposure to environmental irritants. Ranking of symptoms using severity scores was consistent between men and women. Overall scores were higher in women, in participants who were separated or divorced, and in low-income groups. The type and consistency of symptoms experienced after exposure to triggering substances may not fit a purely psychogenic theory.

Self-reported sensitivity to chemical exposures in five clinical populations and healthy controls

Two hundred and twenty-five subjects, including normal volunteers and patients with previously documented seasonal affective disorder (SAD), chronic fatigue syndrome (CFS), Cushing's syndrome, Addison's disease and obsessive-compulsive disorder (OCD), completed a self-rated inventory of reported sensitivity to various chemical exposures. Patients with CFS, Addison's disease and SAD self-reported more sensitivity to chemical exposures than normal controls. In addition, women reported more sensitivity than men. This report suggests that chemical sensitivity may be a relevant area to explore in certain medical and psychiatric populations. A possible relationship between reported chemical sensitivity and hypothalamic-pituitary-adrenal (HPA)-axis functioning is discussed.

Psychosomatic medicine: state of the art

Contemporary psychosomatic medicine must take into consideration developments in psychobiology. The difficulty in accepting dualistic concepts is a serious challenge to positions distinguishing between psychological and 'real' causes of disease. There is more emphasis on life style factors for disease and on the impact of psychosocial factors on illness rather than on disease. The neurophysiological concept of activation or arousal has been important in the development of rational pathophysiological models that describe how sustained arousal may be a pathophysiological factor. For illness, sensitization may be an acceptable psychobiological mechanism underlying very frequently occurring and expensive medical conditions that require medical and economical assistance. One possible alternative to old dynamic concepts is the development of a cognitive arousal theory of stress.

Chemical sensitivity and fatigue syndromes from hypoxia/hypercapnia

The multiple chemical sensitivities syndrome (MCS) and other chronic syndromes causing fatigue, headache and other protean CNS symptoms without observable signs, are proposed to result from hypoxia/hypercapnia (H/H) due to disturbed breathing. The concept is explained in terms of sleep apnea (SA), although H/H could result from causes other than SA. Reasons for considering this etiologic linkage are as follows: 1. MCS symptoms resemble those of SA. 2. The only physical signs associated with MCS (upper airway inflammation and obstruction) can aggravate SA. 3. The only neuropsychiatric finding common among MCS symptomatics, reduced verbal recall, is associated with SA. 4. Many MCS symptomatics attribute onset of their condition to a pesticide or solvent exposure. Solvent neurotoxicity may cause cacosmia, a symptom of MCS and SA. 5. Improved upper airway patency, a first-line therapy in SA, may improve symptoms in some MCS-like conditions. Implications for diagnosis and treatment of MCS are discussed.

Limbically Augmented Pain Syndrome (LAPS): Kindling, Corticolimbic Sensitization, and the Convergence of Affective and Sensory Symptoms in Chronic Pain Disorders

There is abundant clinical evidence that depression occurs with high frequency among chronic pain patients. When compared with other serious medical disorders, the prevalence of depression in chronic pain appears high. The fundamental reason for this association is unknown. Theories have attempted to explain the link between pain and depression in terms of psychologic mechanisms. Other theories highlight shared neurobiologic substrates. However, a comprehensive theory integrating biologic and psychologic viewpoints remains elusive. In this article, we draw on research on neuroplastic processes in corticolimbic structures to model the linkage between the sensory and affective domains of pain. Our hypothesis is based on kindling experiments in animals that elucidate the complex neurobiologic mechanisms that transduce exteroceptive and interoceptive stimuli into "memory" at the cellular/synaptic level. This experimental model has found application in the affective disorders to explain how a person's history of exposure to psychologic trauma configures the neurobiologic substrate for later-amplified pathologic response. In applying kindling research to pain, we begin by reviewing the literature on nociception-induced neuroplasticity at the corticolimbic level. We suggest that kindling and related models of neuroplasticity can be used to describe ways in which exposure to a noxious stimulus may, under certain conditions, lead to a sensitized corticolimbic state. This sensitized state can be described in terms of the kindling properties of amplification, spontaneity, neuroanatomic spreading, and cross-sensitization. A case example illustrates how these properties offer a neurobiologic framework for understanding the sensory/affective/behavioral symptom complex seen in a subset of chronic pain patients. These patients are characterized by atypical and treatment-refractory pain complaints, in association with disturbances of mood, sleep, energy, libido, memory/concentration, behavior, and stress intolerance. We introduce the term "limbically augmented pain syndrome" to describe this symptom complex.

Symptom patterns in long-duration chronic fatigue syndrome

OBJECTIVE

Our objective was to evaluate symptom patterns in patients with chronic fatigue syndrome (CFS) who were ill for 10 or more years.

METHODS

This cross-sectional self-report study compared patient groups with long-duration (median = 18 years; n = 258) and short-duration (median = 3 years; n = 28) CFS to a group of healthy significant others (n = 79) on symptomatic, neurocognitive, and psychological variables. Data were gathered from a 574-item postal questionnaire.

RESULTS

A principal-components analysis of CFS symptom data yielded a three-factor solution: cognitive problems; flu-like symptoms; and neurologic symptoms. Compared with the short-duration CFS group, the long-duration group had significantly higher CFS symptom severity scores (p < 0.04), largely attributable to increased cognitive difficulties. A subgroup comparison of subjects ill for < 3 years versus those ill 4-7 years suggested that denial coping strategies were more likely in those participants with the shorter illness duration. Significant differences between both CFS groups and healthy controls were found in a number of comorbid disorders. Participants with CFS most often endorsed immune/viral abnormalities and persistent stress as important perceived causes of their illness.

CONCLUSION

Participants with long-duration CFS reported a large number of specific cognitive difficulties that were greater in severity than those reported by participants with short-duration CFS. The pattern of comorbid disorders in the CFS groups was consistent with hypersensitivity and viral reactivation hypotheses.

Behavioral sensitization after repeated formaldehyde exposure in rats

Multiple chemical sensitivity (MCS) is a phenomenon whereby individuals report increased sensitivity to chemicals in the environment, and attribute their sensitivities to prior exposure to the same or often structurally unrelated chemicals. A leading hypothesis suggests that MCS is akin to behavioral sensitization observed in rodents after repeated exposure to drugs of abuse or environmental stressors. Sensitization occurring within limbic circuitry of the central nervous system (CNS) may explain the multisymptom complaints in individuals with MCS. The present studies represent the continuing development of an animal model for MCS, the basis of which is the CNS sensitization hypothesis. Three behaviors were assessed in rats repeatedly exposed to formaldehyde (Form) inhalation. In the first series of experiments, rats were given high-dose Form exposure (11 parts per million [ppm]; 1 h/day x 7 days) or low-dose Form exposure (1 ppm; either 1 h/day x 7 days or 1 h/day x 5 days/week x 4 weeks). Within a few days after discontinuing daily Form, cocaine-induced locomotor activity was elevated after high-dose Form or 20 days of low-dose Form inhalation. Approximately 1 month later, cocaine-induced locomotor activity remained significantly elevated in the 20-day Form-exposed rats. The second experiment assessed whether prior exposure to Form (20 days, as above) would alter the ability to condition to an odor (orange oil) paired with footshock. The results suggested a tendency to increase the conditioned fear response to the odor but not the context of the footshock box, and a decreased tendency to extinguish the conditioned fear response to odor. The third experiment examined whether CNS sensitization to daily cocaine or stress would alter subsequent avoidance responding to odor (Form). Daily cocaine significantly elevated approach responses to Form, while daily stress pretreatment produced a trend in the opposite direction, producing greater avoidance of Form. Preliminary studies indicated that repeated daily Form inhalation (20 days, as above) produced a greater avoidance to subsequent Form presentation, suggesting that daily Form inhalation may serve as a stressor. The results support the hypothesis that repeated chemical exposure in rats may produce CNS plasticity manifest as greater sensitivity to dopaminergic drugs, enhanced fear conditioning to odor paired with an aversive event, and greater avoidance of odors. Some of these behavioral changes observed in rats may provide a link with symptoms in a subset of individuals with MCS.

Neural sensitization model for multiple chemical sensitivity: overview of theory and empirical evidence

This paper summarizes theory and evidence for a neural sensitization model of hyperresponsivity to low-level chemical exposures in multiple chemical sensitivity (MCS). MCS is a chronic polysymptomatic condition in which patients report illness from low levels of many different, structurally unrelated environmental chemicals (chemical intolerance, CI). Neural sensitization is the progressive host amplification of a response over time from repeated, intermittent exposures to a stimulus. Drugs, chemicals, endogenous mediators, and exogenous stressors can all initiate sensitization and can exhibit cross-sensitization between different classes of stimuli. The properties of sensitization overlap much of the clinical phenomenology of MCS. Animal studies have demonstrated sensitization to toluene, formaldehyde, and certain pesticides, as well as cross-sensitization, e.g., formaldehyde and cocaine. Controlled human studies in persons with self-reported CI have shown heightened sensitizability in the laboratory to nonspecific experimental factors and to specific chemical exposures. Useful outcome measures include spectral electroencephalography, blood pressure, heart rate, and plasma beta-endorphin. Findings implicate, in part, dopaminergic mesolimbic pathways and limbic structures. A convergence of evidence suggests that persons with MCS or with low-level CI may share some characteristics with individuals genetically vulnerable to substance abuse: (a) elevated family histories of alcohol or drug problems; (b) heightened capacity for sensitization of autonomic variables in the laboratory; (c) increased amounts of electroencephalographic alpha activity at rest and under challenge conditions over time. Sensitization is compatible with other models for MCS as well. The neural sensitization model provides a direction for further systematic human and animal research on the physiological bases of MCS and CI.

Evolutionary game theory and multiple chemical sensitivity

Newlin's [Newlin D.B. Evolutionary game theory of tolerance and sensitization in substance abuse. Paper presented to the Research Society on Alcoholism, Hilton Head, SC, 1998] evolutionary game theory of addictive behavior specifies how evolutionarily stable strategies for survival and reproduction may lead to addiction. The game theory of multiple chemical sensitivity (MCS) assumes that: (1) the MCS patient responds to low-level toxicants as stressors or as direct threats to their survival and reproductive fitness, (2) this activates the cortico-mesolimbic dopamine system, (3) this system is a survival motivation center--not a 'reward center', (4) the subject emits a counter-response that is in the same direction as the naive response to the chemicals, (5) previously neutral stimuli associated with chemicals also trigger conditioned responses that mimic those to the chemicals, (6) these counter-responses further activate the dopaminergic survival motivation system, and (7) this produces a positive feedback loop that leads to strong neural sensitization in these structures and in behavior controlled by this system, despite a small initial response. Psychologically, the MCS patient with a sensitized cortico-mesolimbic dopamine system is behaving as though his/her survival is directly threatened by these chemicals. Non-MCS subjects have counter-responses opposite in direction to those of the chemicals and show tolerance. An autoshaping/sign-tracking model of this game is discussed. This evolutionary game makes several specific, testable predictions about differences between MCS subjects, non-MCS controls, and substance abusers in laboratory experiments, and between sensitized and nonsensitized animals.

Patterns of waking EEG spectral power in chemically intolerant individuals during repeated chemical exposures

Previous studies indicate that low level chemical intolerance (CI) is a symptom of several different controversial conditions with neuropsychiatric features, e.g., chronic fatigue syndrome, fibromyalgia, multiple chemical sensitivity, and "Persian Gulf Syndrome". Prior studies suggest that limbic and/or mesolimbic sensitization may contribute to development of CI. The purpose of this report was to document the waking electroencephalographic (EEG) patterns of individuals with CI during chemical exposures presented over repeated sessions. Three groups of adult subjects who were recruited from the community participated in the study: self-reported CI who had made associated lifestyle changes due to their intolerance (CI/ LSC), self-reported CI who had not made such changes (CI), and normal controls without self-reported CI. Subjects underwent two sessions involving one-minute EEG recordings during exposures to low level chemical odors (a probe for limbic activation). The CI, but not the CI/ LSC, subjects had increased absolute delta power after the chemical exposures during the second, but not the first, session. The findings support the neural sensitization hypothesis for intolerance to low levels of environmental chemicals in vulnerable individuals. As in human studies of stimulant drug sensitization, those with the strongest past history with sensitizing agents may not show-term sensitization to low level exposures in the laboratory.

On the similarity of odor and language perception

The association between olfaction and language is discussed. The effects of odor on human behavior and cognitive processing are reviewed as are electrophysiological studies of odor/language interactions. Also reviewed are specific effects of odor administration on language-dependent tasks. The hypothesis is advanced that odor information processing shares some of the cortical resources used in processing language and that interference between these two types of stimuli occurs when they are simultaneously processed. The reason for this overlap in resources is thought to be due to the similarities in the spatio-temporal patterns produced in the neural coding of odors and language.

The time dimension in stress responses: relevance for survival and health

Within the Cognitive Activation Theory of Stress (CATS), the stress response occurs whenever there is a discrepancy between what the organism is expecting, and what really exists. It affects the biochemistry of the brain, mobilizes resources, affects performance, and endocrine, vegetative, and immune systems. Initial positive feedback and feed-forward mechanisms are gradually changed by homeostatic mechanisms. Slower reactive hormones such as cortisol seem to dampen the initial response. The time course may depend on psychological mechanisms. Subjects with efficient coping show the fast- and short-lasting catecholamine response, while subjects with high defense mechanisms (related to stimulus expectancies) may show more signs of prolonged activation. Non-coping individuals show a sustained general activation which may develop into somatic disease or illness.

The psychology in psychoneuroendocrinology

This paper reviews the psychology (P) of psychoneuroendocrinology (PNE). The relationship between the P factors and the endocrine responses (E) is described within cognitive reformulations of stress theory and activation theory. The formulations are valid across species, including man. The emphasis is on acquired expectancies, which are assumed to determine the physiological response, including the E responses. The terms coping, helplessness, and hopelessness are defined, and related to other labels covering the same or similar phenomena. The implications of contemporary P theory for the typical PNE experimental situations are discussed. Finally, the PNE positions outlined in 1968 by Mason is revisited. The 30 years of PNE research that followed confirm and expand his conclusions.

A critical analysis of multiple chemical sensitivities

Multiple chemical sensitivities (MCS) is a chronic condition of irritation and inflammation of sensory organs, gastrointestinal distress, fatigue, and compromised neurological function, including learning and memory deficits, unpleasant smells, tingling of nerves, and sensory discomfort. Victims report these symptoms after exposure to unfamiliar chemicals. Some studies have linked MCS to immune system dysregulation. MCS is believed to be a disease that spreads between various target organs, and is caused by sensitization to chemicals with very different structures. MCS is often attributed to free radical production and stress, which indirectly cause spreading because of damage to the immune system.

Differential resting quantitative electroencephalographic alpha patterns in women with environmental chemical intolerance, depressives, and normals

BACKGROUND

Previous research suggests that a subset of individuals with intolerance to low levels of environmental chemicals have increased levels of premorbid and/or comorbid psychiatric disorders such as depression, anxiety, and somatization. The purpose of this study was to evaluate the psychological profiles and quantitative electroencephalographic (qEEG) profiles at baseline of women with and without chemical intolerance (CI).

METHODS

Participants were middle-aged women who reported illness from the odor of common chemicals (CI, n = 14), depressives without such intolerances (D, n = 10), and normal controls (N, n = 11). They completed a set of psychological scales and underwent two separate qEEG recording laboratory sessions spaced 1 week apart, at the same time of day for each subject.

RESULTS

CI were similar to D with increased lifetime histories of physician-diagnosed depression (71% vs. 100%), Symptom Checklist 90 (revised) (SCL-90-R) somatization scores, Barsky Somatic Symptom Amplification, and perceived life stressfulness, although D had more distress than either CI or N on several other SCL-90-R subscales. CI scored significantly higher on the McLean Limbic Symptom Checklist somatic symptom subscale than did either D or N. On qEEG, CI exhibited significantly greater overall resting absolute alpha activity with eyes closed, especially at the parietal midline site (Pz), and increased (sensitized) frontal alpha from session 1 to 2, in contrast with the D and N groups. D showed right frontal asymmetry in both sessions, in comparison with CI.

CONCLUSIONS

The data indicate that CI with affective distress diverge from both D without chemical intolerance and N in qEEG alpha patterns at resting baseline. Although CI descriptively resemble D with increased psychological distress, the CI's greater alpha suggests the possibility of a) central nervous system hypo-, not hyper-, activation; and/or b) an overlap with EEG alpha patterns of persons with positive family histories of alcoholism.

Quantitative EEG patterns during nose versus mouth inhalation of filtered room air in young adults with and without self-reported chemical odor intolerances

Individuals who report illness (e.g. nausea, headache) from common chemical odors tend to report CNS symptoms suggestive of olfactory-limbic system involvement. This study compared the resting quantitative electroencephalographic (qEEG) patterns of young adult college students reporting subjectively elevated chemical odor intolerance ratings (HICI) with those of controls reporting little or no odor intolerance (LOCI). Each group was subdivided into those with higher (HIDEP) vs. lower (LODEP) ratings of concomitant depression. Nineteen channels of EEG were recorded during a single session over four separate rest periods, respectively, following baseline, cognitive, chemical exposure and olfactory identification tests. Each recording involved two 30-s, eyes-closed, filtered room air breathing conditions: (1) nose inhalation followed by mouth exhalation and (2) mouth inhalation followed by mouth exhalation. HICI showed significantly less beta 1 (beta 1) over the temporal-central region during nose than during mouth inhalation. Over some temporal and central leads, task, DEP and CI interacted to influence beta 1 as well. For theta (theta), CI differences emerged during nose inhalation after the cognitive task at Cz, after chemical exposures at C3, Cz and C4 and after the olfactory ID task at C4. CI differences emerged during mouth breathing after the olfactory ID task at Cz, C4 and T4. The T5-T6 coronal array showed significant CI differences after chemical exposures during nose breathing and during mouth breathing after the cognitive and olfactory ID tasks. The theta findings in the HICI may be related to reports of disturbed attention in CI.

Sensitization, somatization, and subjective health complaints

More than half of the days lost due to sickness absence are due to diagnostic groups that solely or mainly depend on subjective statements from the patient The most frequent subjective health complaints are musculoskeletal pain. These conditions do not seem to qualify as psychiatric or mental disorders, but are not strictly somatic states either. Terms like somatization may be inadequate terms for states that may be best understood as psychobiological feedback loops. Subjective health complaints is suggested as a neutral, descriptive term. Only a minority requires treatment and sickness compensation for prolonged periods for these very common states. In these patients the neurons in feed-forward and positive feedback loops may have developed sensitization. These patients tend to show an abnormal sensitivity to sensory input from muscles, the gastrointestinal tract, and to smell and taste. It seems to be futile to search for single-factor solutions. This approach opens up for the possible effectiveness of many different types of treatment, breaking the feedback loops.

Time-dependent sensitization of heart rate and blood pressure over multiple laboratory sessions in elderly individuals with chemical odor intolerance

In this study, we tested the hypothesis that low-level chemical odor intolerance (i.e., "cacosmia") is a manifestation of heightened sensitizability to environmental stimuli. We examined supine heart rate and blood pressure of elderly individuals, who were classified as either having a higher degree of chemical odor intolerance (n = 12) or a lower degree of chemical odor intolerance (n = 13), upon awakening in a sleep research laboratory on 6 different days during an 8-wk protocol. During the 2 initial wk, they consumed a customary baseline diet (including ad lib milk and other dairy products), followed by 3 wk each of nondairy-containing and dairy-containing diets in randomly assigned, counterbalanced order. Measurements were made on 3 pairs of successive days, distributed over a 6-wk period, and on which different diets were consumed. The high-intolerance group had significantly higher mean supine systolic and diastolic blood pressures than did the low-intolerance group. Although subjects consumed milk products during both the initial baseline and subsequent dairy diet periods, the high-intolerance group had significantly higher heart rates and diastolic blood pressures later in the study than at baseline, especially when they were on the dairy diet. In contrast, the cardiovascular measures of the low-intolerance group lowered on average with time. The high-intolerance subjects had an increased mean diastolic blood pressure on the second days versus the first days in the laboratory (averaged across all diets). Collectively, the data suggest that elderly individuals with a high degree of chemical odor intolerance evidence (a) increased sympathetic tone in the cardiovascular system at rest over multiple measurements; and (b) greater sensitizability and/or lesser habituation of heart rate and diastolic blood pressure over time as a function, in part, of repeated environmental stressor exposures (i.e., a novel laboratory contextual setting and/or specific dietary constituents). Consistent with a sensitization model, the findings emphasize the need for two or more identical sessions at least 24 h apart in physiological studies of individuals with a high degree of intolerance for chemical odors versus normal individuals. The results of the blood pressure observations suggest that the possibility of abnormally labile autonomic function and cognitive sequelae in individuals with a high degree of intolerance for chemical odor increases with age.

Sensitization induced by kindling and kindling-related phenomena as a model for multiple chemical sensitivity

It has been suggested that the neurobehavioral dysfunction observed in persons presenting with symptoms of Multiple Chemical Sensitivity (MCS) syndrome involves sensitization of neural circuits. Two hypotheses for the route of exposure in induction of neural sensitization in MCS are: (a) direct chemical stimulation of olfactory processes, or (b) general systemic response to inhaled chemicals. In either case, the mechanism of action may involve chemical kindling or kindling-related phenomena. A neural sensitization mechanism based on kindling or kindling-related phenomena is attractive and has been previously demonstrated in both in vitro and in vivo animal models. Without a testable animal model for chemically mediated induction of MCS, however, any argument that MCS is mediated by kindling or kindling-related phenomena is reduced to the circular argument "the mechanism of sensitization is sensitization." The present survey provides an overview of the experimental paradigms that result in sensitization, differentiated on the basis of probable neurophysiological and neurochemical mechanisms. Neurophysiological potentiation, electrical kindling, chemical kindling and behavioral sensitization are evaluated and discussed in relationship to MCS.

Clinically relevant EEG studies and psychophysiological findings: possible neural mechanisms for multiple chemical sensitivity

This paper addresses the evidence for the face, construct, and criterion-related validity of the olfactory-limbic/neural sensitization model for multiple chemical sensitivity (MCS). MCS is a poorly-understood, controversial condition in which low levels of environmental chemicals are reported to trigger disabling levels of illness in certain individuals. Neural sensitization processes could generate an endogenous amplification of responsivity to exogenous substances, thereby providing a plausible explanation for the apparent lack of a classical toxicological dose-response relationship in MCS. Convergent data from both survey and psychophysiological studies of MCS patients and of persons from the community without MCS, but who report elevated frequency of illness from chemical odors (cacosmics), support the involvement of the limbic system and the sensitizability of cacosmics, as predicted by the model. Recent studies show that cacosmics do sensitize their heart rate, blood pressure, and plasma beta-endorphin responses to repeated exposures to a novel laboratory procedure involving dietary manipulations over time. Cacosmia may represent a pathological form of neural plasticity. Taken together, the model and the available evidence suggest the need for more intensive investigation of MCS from the standpoint of possible neurobiological mechanisms affecting cognitive, emotional, and somatic functions.

Proposed animal neurosensitization model for multiple chemical sensitivity in studies with formalin

A potentially promising line of animal research relevant to multiple chemical sensitivity (MCS) is that of sensitization in the central nervous system (CNS), particularly limbic pathways in the brain. Sensitization is the progressive and enduring enhancement in behavioral and neurochemical responses that occurs after repeated exposure to psychostimulants or environmental stressors. Since the onset and progression of sensitization has many parallels with that of MCS, it has been proposed that MCS may be initiated through a mechanism similar to the sensitization of CNS components occurring in the rodent. To test this hypothesis, female Sprague-Dawley rats were exposed to formalin vapors (FORM, 11 ppm) or water vapor (control) 1 h/day for 7 days. The next day, a saline injection was given followed by a cocaine injection (15 mg/kg, i.p.) 24 h later, and locomotor activity was monitored. Animals pretreated with repeated FORM inhalation demonstrated a significantly enhanced locomotor response to cocaine compared to controls, an indicator that specific limbic pathways may have been sensitized. At 4 weeks of withdrawal from FORM exposure, a subset of animals remained sensitized to a cocaine challenge. No differences were found between groups after a saline injection. In a second experiment, animals were screened prior to FORM or water exposure for their response to a novel situation, a measure believed to reflect an animal's general responsiveness to stimuli. Rats were divided into high responders (HR) or low responders (LR), based on their locomotion in a novel cage. Results from three behavioral tests demonstrated that HR and LR were differentially affected by exposure to FORM. In a passive avoidance test, HR and LR appeared to be different in their distribution of responses, while HR and LR responses in the FORM group were nearly identical. On the elevated plus maze test of anxiety, HR spent more time on the open arms than LR in both treatment groups, with significant differences between HR and LR in the FORM, but not water, treated group. On a hot plate test to measure nociceptive levels, no differences occurred between HR and LR in the control group, whereas nociception of LR tended toward an increase compared to HR in the FORM-exposed group. Results from the second experiment suggest that the effects of FORM exposure may be obscured by examining behavior in a heterogeneous population (HR and LR). This approach using animal models may help define neural substrates that mediate the amplification of responses of a subpopulation of individuals to chemicals in the environment.

A polysomnographic study of sleep disturbance in community elderly with self-reported environmental chemical odor intolerance

Subjective sleep complaints and food intolerances, especially to milk products, are frequent symptoms of individuals who also report intolerance for low-level odors of various environmental chemicals. The purpose of the present study was to evaluate the objective nature of nocturnal sleep patterns during different diets, using polysomnography in community older adults with self-reported illness from chemical odors. Those high in chemical odor intolerance (n = 15) exhibited significantly lower sleep efficiency (p = .005) and lower rapid-eye-movement (REM) sleep percent (p = .04), with a trend toward longer latency to REM sleep (p = .07), than did those low in chemical intolerance (n = 15), especially on dairy-containing as compared with nondairy (soy) diets. The arousal pattern of the chemical odor intolerant group differed from the polysomnographic features of major depression, classical organophosphate toxicity, and subjective insomnia without objective findings. The findings suggest that community elderly with moderate chemical odor intolerance and minimal sleep complaints exhibit objectively poorer sleep than do their normal peers. Individual differences in underlying brain function may help generate these observations. The data support the need for similar studies in clinical populations with chemical odor intolerance, such as multiple chemical sensitivity patients and perhaps certain veterans with "Persian Gulf Syndrome."

Time-dependent sensitization of plasma beta-endorphin in community elderly with self-reported environmental chemical odor intolerance

This study examined plasma beta-endorphin as a marker of the physiological stress response in community elderly who were either high (n = 15) or low (n = 15) in self-rated frequency of illness from environmental chemical odors. Individuals who report nonatopic multiple sensitivities to or intolerances for low levels of environmental chemicals also claim high rates of comorbid food sensitivities or intolerances. Subjects gave 9 AM blood samples for plasma beta-endorphin 90 min after ingesting either 1% fat cow's milk or a soy-based nondairy drink, on six different mornings in the laboratory after all-night sleep recordings. The six sessions-were divided into three sets of two successive days each, with each set [involving baseline (ad lib milk), nondairy (soy-based), and dairy diets] separated from the next by 3 weeks. In the chemically tolerant subjects, stably lower beta-endorphin levels suggested that milk may have been a physiologically less stressful beverage than was the soy drink. In contrast, the chemical odor intolerant group exhibited a) increased levels of plasma beta-endorphin averaged over the 6 days (p = .02); and b) marked fluctuations in endorphin from one laboratory day to the next (Group x Diet x Day interaction, p = .005). The findings were consistent with time-dependent, context-dependent sensitization of beta-endorphin in the chemical odor intolerant individuals.

Slowed reaction time performance on a divided attention task in elderly with environmental chemical odor intolerance

Previous research has suggested an association between the subjective report of illness from environmental chemical odors and poorer cognitive task performance in persons with industrial levels of xenobiotic exposures. The present study investigated baseline morning performance on a computerized divided attention task in active retired adults without occupational exposures or clinical disorders who nonetheless rated themselves currently high versus low in episodic illness from the odor of certain environmental chemicals. The chemically intolerant group showed slower reaction times in registering both centrally and peripherally placed stimuli, but no difference in making target tracking errors. Measures of negative affect did not account for these findings. Taken together with evidence for heightened neurobehavioral sensitization in this population, the data suggest disturbances in allocation of attention and related cognitive functions.

Neuropsychiatric and somatic characteristics of young adults with and without self-reported chemical odor intolerance and chemical sensitivity

The psychological, neuropsychiatric, and somatic characteristics of young adults who have different degrees of cacosmia (i.e., feeling "ill" from the odor of xenobiotic chemicals) and who have self-described "chemical sensitivity" were examined. A total of 800 college students completed the following: a self-rating scale for frequency of odor intolerance for 10 common substances, Simon Environmental Illness Symptom Survey, the SCL-90-R, Barsky Amplification Scale, Pearlin-Schooler Mastery Scale, Cheek-Buss and Kagan Shyness scales, Marlowe-Crowne Social Desirability Scale, and a health-symptom and physician-diagnosed checklist. Two pairs of groups were compared: (1) subjects in the top 16% (i.e., cacosmics) and bottom 15% (noncacosmics) of the sample with respect to odor intolerance scale scores; and (2) subjects from the entire sample who did (28%) or did not (72%) consider themselves to be "especially sensitive to certain chemicals.¿ Cacosmics and the chemically sensitive subjects scored significantly higher on measures of psychological distress and amplification of somatic symptoms, but there was little evidence of lifestyle change, as assessed by the Simon Survey. Compared with their respective comparison groups, cacosmic and chemically sensitive groups had significantly higher incidences of illnesses associated with chemicals, alcohol intake, opiate drug use, and caffeine use, even after controlling for the psychological measures and histories of atopic allergy. Subjects with and without neuropsychiatric symptoms were differentiated with respect to chemical odor intolerance, but subjects with and without atopic allergies and possible autoimmune diseases were differentiated with respect to chemical sensitivity. Females were more cacosmic than males. Cacosmia is defined by a population subset, with or without occupational xenobiotic exposures or disability, that has distress and symptom amplification and neuropsychiatric and somatic symptoms, none of which are explained fully by psychological measures. Prospective clinical studies are possible with such individuals. The data are also consistent with a time-dependent sensitization model for illness from low-level chemical exposures.

Nasal pathology and ultrastructure in patients with chronic airway inflammation (RADS and RUDS) following an irritant exposure

BACKGROUND

Reactive airways dysfunction syndrome is a chronic asthma-like condition developing after an acute irritant exposure, and chronic inflammation has been seen on endobronchial biopsy. Reactive upper-airways dysfunction syndrome is chronic rhinitis developing in temporal association with a toxic inhalation exposure, but the pathophysiology is unknown.

OBJECTIVES

To study biopsies of the nasal mucosa in patients with reactive upper-airways dysfunction syndrome and in some cases reactive airways dysfunction syndrome developing in temporal association with a chlorine dioxide exposure, to see if a histologic basis for the persistent rhinitis and sensitivity to chemical irritants could be determined.

METHODS

Specimens were stained with hematoxylin-eosin and immunoperoxidase stains for substance P, vasointestinal peptide, and S-100 (nerve fibers), and fixed in glutaraldehyde for electron microscopy. Biopsies of three nonexposed subjects were performed for comparison. A pathologist blinded to clinical data interpreted the specimens.

RESULTS

Inflammation ratings of exposed individuals were higher than for the nonexposed individuals. The number of nerve fibers stained was greater for patients vs controls. Substance P and vasointestinal peptide staining was nonspecific. Electron microscopy showed desquamation of the epithelium and permeability of epithelial cell junctions.

CONCLUSION

This study suggests a mechanism by which ongoing low level exposures perpetuate airway inflammation after an inducing toxic inhalation. A possible overlap between reactive airways dysfunction syndrome, reactive upper-airway dysfunction syndrome and the multiple chemical sensitivity syndrome is suggested.