Study of the Correlation Between Multiple Chemical Sensitivity and Personality Using the Quick Environmental Exposure Sensitivity Inventory Questionnaire and the Temperament and Character Inventory.

OBJECTIVE: We conducted an analysis using the Quick Environmental Exposure Sensitivity Inventory to examine the correlation between multiple chemical sensitivity (MCS) and personality traits by using temperament and character inventory, and environmental exposures. METHODS: An anonymous questionnaire was distributed to 667 employees working at an IT manufacturing plant in Japan. Variables including chemically sensitive population (CSP), personality, and environmental chemical exposure were individually evaluated using U-test, chi-squared test, and correlation analyses. We also did covariance structure analysis to build a structural equation model. RESULTS: There was little direct impact of temperament on the CSP, while there was a significant impact of character on the CSP. Women were more likely to exhibit symptoms of CSP. CONCLUSION: MCS is correlated with personality, impacted more by character acquired later in life than innate temperament. There were sex differences in the incidence of MCS.

Multiple chemical sensitivity: pursuit of a scientific consensus, need for a public health response. Commentary.

On the international scene, Multiple Chemical Sensitivity (MCS) is defined, by several experts, as a multisystem syndrome that develops following chronic exposures to low doses of common chemical contaminants. Its general characteristics are, however, the object of conflicting opinions and a source of debate and research aimed at the appropriate nosological and therapeutic frameworks. In the face of a potentially debilitating trend, both in the occupational and in the economical and social sphere, the scientific community has not so far found an agreement. This problem leads patients and their associations to periodically claim some requests. The syndrome is also taken into consideration at a political level, especially due to the close connection with the problems related to environmental pollution and to decision making in the field of control and prevention. For these reasons we believe that an appropriate widespread surveillance network for MCS should be set up in Italy, capable of intercepting possible cases, analyzing them at a multidisciplinary level, and following their evolution.

Chemical intolerance: involvement of brain function and networks after exposure to extrinsic stimuli perceived as hazardous.

BACKGROUND: Chemical intolerance (CI) is a chronic condition characterized by recurring and severe symptoms triggered by exposure to low levels of odorous or pungent substances. The etiology of CI has been a controversial subject for a long time. The aim of this review is to summarize findings on the neurological processing of sensory information during and after exposure to low levels of odorous or pungent substances in individuals with CI, focusing on the brain function and networks. METHODS: Scientific studies on CI published between 2000 and 2019 in academic peer-reviewed journals were systematically searched using medical and scientific literature databases. Only peer-reviewed articles reporting original research from experimental human studies directly associated with CI, and involving related neurological responses or brain imaging after exposure to odorous or pungent substances (i.e., in chemical provocation tests), were considered. RESULTS: Forty-seven studies were found to be eligible for a full-text review. Twenty-three studies met the selection criteria and were included in this review. Evidence indicated that differences between subjects with CI and healthy controls were observed by brain imaging during and after exposure to odorous or pungent substances. Differences in brain imaging were also observed between initial exposure and after exposure to these substances. Neurological processing of sensory information after exposure to extrinsic stimuli in the limbic system and related cortices were altered in subjects with CI. A previous documentable exposure event was likely to be involved in this alteration. CONCLUSIONS: This review documents consistent evidence for the altered neurological processing of sensory information in individuals with CI. Further neurophysiological research exploring the processing of extrinsic stimuli and cognition of sensation through the limbic system and related cortices in CI, and the appearance of symptoms in individuals with CI, are required.

Modern health worries: A systematic review.

OBJECTIVE: Modern health worries (MHWs) refer to people's concerns about possible harmful effects of modern technologies, and are widespread in the developed countries. The aim of the present work was to provide comprehensive, yet integrated understanding for MHWs and associated factors. METHODS: Following the PRISMA guideline, a systematic review was conducted based on 48 empirical articles published between 2001 and 2018 (Prospero registration number: CRD42018103756). All empirical studies were included that (1) were published between 2001 and 2018 in peer-reviewed scientific journals in English, German, or Hungarian, (2) used the Modern Health Worries Scale or any of its sub-scales, and (3) assessed associations between MHWs and other constructs and/or compared criterion groups (i.e. purely psychometric studies were excluded). RESULTS: The results from the review suggest that female gender, age, somatic symptom distress and idiopathic environmental intolerances, holistic thinking, and paranoid beliefs are positively associated with MHWs, whereas educational qualification and the five major dimensions of personality appear not to be. CONCLUSION: Scientific inquiry on the MHWs phenomenon is still in its descriptive-explorative phase; more rigorously designed studies are needed. The presented theoretical framework integrates illness-related and holistic thinking-related aspects of MHWs as a starting point to guide further research in this area.

Somatosensory amplification absorption contribute to electrosensitivity.

BACKGROUND AND PURPOSE: Two trait-like characteristics, somatosensory amplification and absorption, have been associated with symptom reports and idiopathic environmental intolerances in past research. Purpose - As the two constructs are not connected with each other, their independent contribution to symptom reports and electromagnetic hypersensitivity, as well as their interaction can be expected. METHODS: On-line questionnaire. Patients - 506 college students completed an on-line questionnaire assessing absorption, somatosensory amplification, negative affect, somatic symptoms, and electromagnetic hypersensitivity. RESULTS: Somatosensory amplification (ß = 0.170, p < 0.001) and absorption (ß = 0.128, p < 0.001) independently contributed to somatic symptoms after controlling for gender and negative affect (R2 = 0.347, p < 0.001). Similarly, somatosensory amplification (OR = 1.082, p < 0.05) and absorption (OR = 1.079, p < 0.01) independently contributed to electromagnetic hypersensitivity after controlling for somatic symptoms, gender, and negative affect (Nagelkerke R2 = 0.134, p < 0.001). However, no interaction effects were found. CONCLUSION: Somatosensory amplification and absorption independently contribute to symptom reports and electromagnetic hypersensitivity. Conclusion - The findings suggest that psychological mechanisms underlying symptom reports and electromagnetic hypersensitivity might be heterogeneous.

Perspectives on multisensory perception disruption in idiopathic environmental intolerance: a systematic review.

PURPOSE: Multiple chemical sensitivity (MCS) also known as idiopathic environmental intolerance/illness (IEI) encompasses a cohort of subjective symptoms characterized by susceptibility to a wide spectrum of environmental compounds, causing symptoms involving various organs and a decrease in quality of life. The aim of this systematic review is to summarize evidence about MCS, with focus on indexed studies analyzing sensory pathway-related disorders. METHODS: Medical databases were searched for English language articles related to the topic, published between 1965 and 2017 in academic, peer-reviewed journals. Particular focus was concentrated on articles depicting disturbances involving sensory organs. References of the relevant articles were examined to identify additional significant documents. RESULTS: Fifty-eight studies were eligible for full text review. Of these, 34 studies met the selection criteria and were included in this analysis. Many variables, such as different diagnostic criteria, lack of homogeneous symptom questionnaires and the general incidence of personality traits in control subjects, biased studies as confounding factors. However, moderate evidences show that sensory pathways are somewhat altered, especially with respect to information processing in the limbic system and related cortical areas. Recent studies suggested the presence, in MCS cohorts, of attention bias, sensitization and limbic kindling, as well as recently revealed subclinical organic alterations along sensory pathways. CONCLUSIONS: Evidences are consistent with MCS/IEI to be the result of a neural altered processing of sensorial ascending pathways, which combined with peculiar personality traits constitutes the underpinning of a multisensory condition needing multidisciplinary clinical approach.

Can explicit suggestions about the harmfulness of EMF exposure exacerbate a nocebo response in healthy controls?

While there has been consistent evidence that symptoms reported by individuals who suffer from Idiopathic Environmental Intolerance attributed to Electromagnetic Fields (IEI-EMF) are not caused by EMF and are more closely associated with a nocebo effect, whether this response is specific to IEI-EMF sufferers and what triggers it, remains unclear. The present experiment tested whether perceived EMF exposure could elicit symptoms in healthy participants, and whether viewing an 'alarmist' video could exacerbate a nocebo response. Participants were randomly assigned to watch either an alarmist (N = 22) or control video (N = 22) before completing a series of sham and active radiofrequency (RF) EMF exposure provocation trials (2 open-label, followed by 12 randomized, double-blind, counterbalanced trials). Pre- and post-video state anxiety and risk perception, as well as belief of exposure and symptom ratings during the open-label and double-blind provocation trials, were assessed. Symptoms were higher in the open-label RF-ON than RF-OFF trial (p < .001). No difference in either symptoms (p = .183) or belief of exposure (p = .144) was observed in the double-blind trials. Participants who viewed the alarmist video had a significant increase in symptoms (p = .041), state anxiety (p < .01) and risk perception (p < .001) relative to the control group. These results reveal the crucial role of awareness and belief in the presentation of symptoms during perceived exposure to EMF, showing that healthy participants exhibit a nocebo response, and that alarmist media reports emphasizing adverse effects of EMF also contribute to a nocebo response.

Multiple Chemical Sensitivity: Review of the State of the Art in Epidemiology, Diagnosis, and Future Perspectives.

OBJECTIVE: Systematic bibliography analysis of about the last 17 years on multiple chemical sensitivity (MCS) was carried out in order to detect new diagnostic and epidemiological evidence. The MCS is a complex syndrome that manifests as a result of exposure to a low level of various common contaminants. The etiology, diagnosis, and treatment are still debated among researchers. METHOD: Querying PubMed, Web of Science, Scopus, Cochrane library, both using some specific MESH terms combined with MESH subheadings and through free search, even by Google. RESULTS: The studies were analyzed by verifying 1) the typology of study design; 2) criteria for case definition; 3) presence of attendances in the emergency departments and hospital admissions, and 4) analysis of the risk factors. OUTLOOK: With this review, we give some general considerations and hypothesis for possible future research.

(In)Visibility Online: The Benefits of Online Patient Forums for People with a Hidden Illness: The Case of Multiple Chemical Sensitivity (MCS).

Sufferers of medically unexplained conditions that are not observable in the clinic can experience multiple layers of invisibility: a lack of biomedical diagnosis; legal skepticism; political disinterest; and a loss of their prior social identity. For those with environmental sensitivities, this is compounded by literal hiddenness due to often being housebound. Drawing on an online survey of people with multiple chemical sensitivity, this article examines how the everyday experience of invisibility is mitigated by engaging with other patients online. Respondents used online forums to undertake various forms of "visibility work," including attempts to crystallize their suffering into something recognizable medically, legally, and politically, and to reconstruct an identity considered valid and deserving-although the therapeutic potential of online support was contingent on intra-group politics. This study demonstrates that online forums allow biomedicine's "invisible others" to struggle for alternative forms of recognition beyond the clinical gaze.

Are media reports able to cause somatic symptoms attributed to WiFi radiation? An experimental test of the negative expectation hypothesis.

People suffering from idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) experience numerous non-specific symptoms that they attribute to EMF. The cause of this condition remains vague and evidence shows that psychological rather than bioelectromagnetic mechanisms are at work. We hypothesized a role of media reports in the etiology of IEI-EMF and investigated how somatosensory perception is affected. 65 healthy participants were instructed that EMF exposure can lead to enhanced somatosensory perception. Participants were randomly assigned to watch either a television report on adverse health effects of EMF or a neutral report. During the following experiment, participants rated stimulus intensities of tactile (electric) stimuli while being exposed to a sham WiFi signal in 50% of the trials. Sham WiFi exposure led to increased intensity ratings of tactile stimuli in the WiFi film group, especially in participants with higher levels of somatosensory amplification. Participants of the WiFi group reported more anxiety concerning WiFi exposure than the Control group and tended to perceive themselves as being more sensitive to EMF after the experiment compared to before. Sensational media reports can facilitate enhanced perception of tactile stimuli in healthy participants. People tending to perceive bodily symptoms as intense, disturbing, and noxious seem most vulnerable. Receiving sensational media reports might sensitize people to develop a nocebo effect and thereby contribute to the development of IEI-EMF. By promoting catastrophizing thoughts and increasing symptom-focused attention, perception might more readily be enhanced and misattributed to EMF.

Differences in psychological and somatic symptom cluster score profiles between subjects with Idiopathic environmental intolerance, major depression and schizophrenia.

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.

Association of Odor Thresholds and Responses in Cerebral Blood Flow of the Prefrontal Area during Olfactory Stimulation in Patients with Multiple Chemical Sensitivity.

Multiple chemical sensitivity (MCS) is a disorder characterized by nonspecific and recurrent symptoms from various organ systems associated with exposure to low levels of chemicals. Patients with MCS process odors differently than controls do. Previously, we suggested that this odor processing was associated with increased regional cerebral blood flow (rCBF) in the prefrontal area during olfactory stimulation using near-infrared spectroscopic (NIRS) imaging. The aim of this study was to investigate the association of odor thresholds and changes in rCBF during olfactory stimulation at odor threshold levels in patients with MCS. We investigated changes in the prefrontal area using NIRS imaging and a T&T olfactometer during olfactory stimulation with two different odorants (sweet and fecal) at three concentrations (zero, odor recognition threshold, and normal perceived odor level) in 10 patients with MCS and six controls. The T&T olfactometer threshold test and subjective assessment of irritating and hedonic odors were also performed. The results indicated that the scores for both unpleasant and pungent odors were significantly higher for those for sweet odors at the normal perceived level in patients with MCS than in controls. The brain responses at the recognition threshold (fecal odor) and normal perceived levels (sweet and fecal odors) were stronger in patients with MCS than in controls. However, significant differences in the odor detection and recognition thresholds and odor intensity score between the two groups were not observed. These brain responses may involve cognitive and memory processing systems during past exposure to chemicals. Further research regarding the cognitive features of sensory perception and memory due to past exposure to chemicals and their associations with MCS symptoms is needed.

Psychological symptoms and health-related quality of life in idiopathic environmental intolerance attributed to electromagnetic fields.

OBJECTIVE: Need for better understanding of the etiology of idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF) motivated the present study of psychological symptoms and health-related quality of life (HRQoL) in person who attribute health problems to electromagnetic fields. METHODS: Participants with IEI-EMF (n=114) and a population-based sample of referents (n=104) were investigated with six subscales of the Symptom Checklist 90 (SCL-90) to assess psychological symptoms, and with eight subscales of the Short Form (36) Health Survey (SF-36) to assess HRQoL. RESULTS: Significantly higher scores were found on obsessive/compulsive behavior, interpersonal hypersensitivity, hostility, phobic anxiety, paranoid thoughts in the IEI-EMF group compared to referents, whereas only a tendency of such a difference was found for psychotism. Furthermore, poorer HRQoL in the IEI-EMF group, compared to referents, were found regarding physical and social functioning, physical and emotional role limitations, general health, vitality, bodily pain, and mental health. Significant correlation with moderate to strong effect sizes were found between several of the SCL-90 and SF-36 subscales. CONCLUSION: The results suggest that IEI-EMF is associated with various types of psychological symptoms and with poor HRQoL. Clinical implications include theoretical support for cognitive behavioral therapy, and, although further research is needed, that attention should be directed towards feelings of inferiority and uneasiness in relationships as well as anger, hostility and resentment towards other people.

Dispositional aspects of body focus and idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF).

Body focus is often considered an undesirable characteristic from medical point of view as it amplifies symptoms and leads to higher levels of health anxiety. However, it is connected to mindfulness, well-being and the sense of self in psychotherapy. The current study aimed to investigate the contribution of various body focus related constructs to acute and chronic generation and maintenance of medically unexplained symptoms (MUS). Thirty-six individuals with idiopathic environmental intolerance to electromagnetic fields (IEI-EMF) and 36 controls were asked to complete questionnaires assessing negative affect, worries about harmful effects of EMFs, health anxiety (HA), body awareness, and somatosensory amplification (SSA), and to report experienced symptoms evoked by a sham magnetic field. Body awareness, HA, SSA, and EMF-related worries showed good discriminative power between individuals with IEI-EMF and controls. Considering all variables together, SSA was the best predictor of IEI-EMF. In the believed presence of a MF, people with IEI-EMF showed higher levels of anxiety and reported more symptoms than controls. In the IEI-EMF group, actual symptom reports were predicted by HA and state anxiety, while a reverse relationship between symptom reports and HA was found in the control group. Our findings show that SSA is a particularly important contributor to IEI-EMF, probably because it is the most comprehensive factor in its aetiology. IEI-EMF is associated with both a fear-related monitoring of bodily symptoms and a non-evaluative body focus. The identification of dispositional body focus may be relevant for the management of MUS.

Sensibilidad química múltiple: evaluación clínica de la gravedad y perfil psicopatológico / Multiple chemical sensitivity: Clinical evaluation of the severity and psychopathological profile

Introducción y objetivo: La sensibilidad química múltiple (.SQM) es un trastorno multisistémico de etiología controvertida que afecta a algunos sujetos al exponerse a productos químicos a concentraciones no perjudiciales. El objetivo de este trabajo es describir las características epidemiológicas, clínicas y psicológicas de una muestra de pacientes con SQM, para un posterior tratamiento grupal específico. Pacientes y método: Estudio descriptivo de los pacientes diagnosticados de SQM en una unidad de toxicología, mediante la administración del cuestionario Quick Environmental Exposure and Sensitivity Inventory, junto con la entrevista estructurada SCID-II, la escala de ansiedad HAS y el test de personalidad tipo A, PCTA. Resultados: Se incluyeron 73 pacientes, con una edad media de 52,6 años (rango 33-77; DE 9,29), siendo 66 mujeres (90,4%). El 53% estaban clasificados como grado i-ii y ii. Sesenta y un pacientes (83%) presentaron algún tipo de comorbilidad, fundamentalmente dolor crónico, fibromialgia y fatiga crónica, con niveles de ansiedad mayores (puntuación media 19,2), predominio de rasgos de personalidad fóbico-evitativo y patrón de conducta tipo A (31,1%). Conclusiones: La SQM afecta principalmente a mujeres de mediana edad, con comorbilidades (dolor crónico, fibromialgia y fatiga crónica), elevada ansiedad y conductas de evitación. Este análisis previo debería ayudar a ofrecer un abordaje psicoterapéutico específico a estos pacientes (AU)

Introduction and objective: Multiple chemical sensitivity (MCS) is a multisystem disorder of controversial etiology, affecting some subjects when exposed to chemicals at no harmful concentrations. The objective of this paper is to describe the epidemiological, clinical and psychological features of a sample of patients with MCS for further specific group treatment. Patiens and method: Descriptive study of patients diagnosed with MCS in a toxicology unit. We administered the Quick Environmental Exposure and Sensitivity Inventory, the structured interview SCID-II, the anxiety scale HAS and the type A personality test, PCTA. Results: Seventy-three patients were included. The mean age was 52,6 years (range 33-77; SD 9.29). Sixty-six were females (90.4%). Fifty-three percent were classified as i-ii and ii grade. Sixty-one patients (83%) presented some type of comorbidity, mainly chronic pain, fibromyalgia and chronic fatigue. They exhibited higher levels of anxiety (average score of 19.2), prevalence of phobic-avoidant traits of personality and type A behavior in 31.1%. Conclusions: MCS affects middle-aged women with comorbidities (chronic pain, fibromyalgia and chronic fatigue) and high anxiety and avoidance behaviors. This preliminary analysis should help provide a specific therapeutic approach to these patients (AU)

[Multiple chemical sensitivity: Clinical evaluation of the severity and psychopathological profile]. / Sensibilidad química múltiple: evaluación clínica de la gravedad y perfil psicopatológico.

INTRODUCTION AND OBJECTIVE: Multiple chemical sensitivity (MCS) is a multisystem disorder of controversial etiology, affecting some subjects when exposed to chemicals at no harmful concentrations. The objective of this paper is to describe the epidemiological, clinical and psychological features of a sample of patients with MCS for further specific group treatment. PATIENS AND METHOD: Descriptive study of patients diagnosed with MCS in a toxicology unit. We administered the Quick Environmental Exposure and Sensitivity Inventory, the structured interview SCID-II, the anxiety scale HAS and the type A personality test, PCTA. RESULTS: Seventy-three patients were included. The mean age was 52,6 years (range 33-77; SD 9.29). Sixty-six were females (90.4%). Fifty-three percent were classified as i-ii and ii grade. Sixty-one patients (83%) presented some type of comorbidity, mainly chronic pain, fibromyalgia and chronic fatigue. They exhibited higher levels of anxiety (average score of 19.2), prevalence of phobic-avoidant traits of personality and type A behavior in 31.1%. CONCLUSIONS: MCS affects middle-aged women with comorbidities (chronic pain, fibromyalgia and chronic fatigue) and high anxiety and avoidance behaviors. This preliminary analysis should help provide a specific therapeutic approach to these patients.

Mindfulness-based cognitive therapy (MBCT) for multiple chemical sensitivity (MCS): Results from a randomized controlled trial with 1 year follow-up.

OBJECTIVE: Multiple chemical sensitivity (MCS) is a medically unexplained condition characterized by symptoms from multiple organ systems following the perception of common odorants. The condition can cause severe functional impairment for afflicted individuals. The aim of this study was to assess the effects of mindfulness-based cognitive therapy (MBCT) for individuals with MCS. METHODS: The intention-to-treat sample (ITT) included 69 individuals who had been randomized to either MBCT or treatment as usual (TAU). The primary outcome measure was the Quick Environmental Exposure and Sensitivity Inventory (QEESI), which measures the following aspects of MCS: impact of MCS on daily life, symptoms, and reactions following chemical exposures. Secondary outcome measures included the Brief Illness Perception Questionnaire (BIPQ) and the anxiety and depression subscales of the symptom checklist 92 (SCL-92). Participants were assessed at baseline and post treatment, and at follow-up periods of 6- and 12-months. RESULTS: We found no effect of MBCT on the primary outcome, nor did we find an effect on levels of depression or anxiety. We did, however, find positive changes in illness perceptions, which were sustained at 12-month follow-up. Dropout rates were low, suggesting MBCT was well received and regarded as an acceptable intervention by individuals with MCS. CONCLUSIONS: Overall, these results suggest that MBCT does not change overall illness status in individuals with MCS, but that MBCT positively changes emotional and cognitive representations. Possible explanations for these results are discussed.

Is There a Connection Between Electrosensitivity and Electrosensibility? A Replication Study.

BACKGROUND: Among people with idiopathic environmental intolerance attributed to electromagnetic fields (IEI-EMF), a better than random detection ability for a 50-Hz 0.5-mT magnetic field (MF) and a propensity to experience more symptoms than controls was reported in a previous study. PURPOSE: The current study aimed to replicate and clarify these results using a modified experimental design. METHOD: Participants of the provocation experiment were 49 individuals with self-reported IEI-EMF and 57 controls. They completed the questionnaires (symptom expectations, Somatosensory Amplification Scale--SSAS, radiation subscale of the Modern Health Worries Scale--MHWS Radiation) and attempted to detect the presence of the MF directed to their right arm in 20 subsequent 1-min sessions. Symptom reports were registered after each session. RESULTS: Individuals with IEI-EMF as opposed to the control group showed a higher than random detection performance (d' index of signal detection theory), while no difference in their bias (ß index) toward the presence of the MF was found. Predictors of reported symptoms were self-reported IEI-EMF and believed as opposed to actual presence of the MF. People with IEI-EMF reported significantly more symptoms particularly in the believed presence of the MF. IEI-EMF was closely related to MHWS Radiation and SSAS scores. CONCLUSION: People with IEI-EMF might be able to detect the presence of the MF to a small extent; however, their symptom reports are connected to perceived exposure.

Negative affect is associated with development and persistence of chemical intolerance: a prospective population-based study.

OBJECTIVE: Chemical intolerance (CI) is characterised by negative health effects attributed to a heightened responsiveness to common airborne chemicals. This longitudinal study explored the hypothesised role of negative affect in the development and persistence of CI in a general population. METHODS: A general population sample aged 19 to 72 years was examined in 2006-2008 and again in 2011-2012. Longitudinal data on CI were analysed with the purpose of examining baseline negative affect as a risk factor for having developed CI at 5-year follow-up and for reporting persistent CI. Participants were classified as reporting no signs of CI, having symptoms of CI and as being a likely CI case based on self-reported reactions to 11 common chemical exposures, symptoms related to chemical exposures and daily life adjustments attributed to reactions when exposed to chemicals. RESULTS: A total of 69.4% of the participants who had reported CI at baseline also reported CI at follow-up. In participants with no baseline CI, 15.5% reported CI at follow-up and 18.1% reported symptoms related to chemicals but no daily life adjustments. Baseline negative affect was positively and statistically significantly associated with both development and persistence of CI. CONCLUSIONS: Initial reports of CI were found to be persistent over time, and a considerable proportion of the participants with no CI at baseline reported having developed CI after 5 years. The positive association between negative affect and CI at the 5-year follow-up supports negative affect as a possible risk factor for CI.