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ORIGINAL ARTICLES |
From the Department of Clinical Psychology, Central Institute of Mental Health, Mannheim, Germany (J.B., M.W., C.P.); Department of Dermatology, University Hospital of Mannheim, Germany (C.B.); Psychological Institute I, University of Münster, Germany (F.R.).
Address correspondence and reprint requests to Josef Bailer, PhD, Central Institute of Mental Health, Department of Clinical Psychology, PO Box 122120, 68072 Mannheim, Germany, Federal Republic of Germany. E-mail: bailer{at}zi-mannheim.de
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ABSTRACT |
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Methods: We compared 54 subjects with IEI, 54 subjects with SFD but without IEI, and 44 subjects with neither IEI nor SFD on symptom scales, psychological questionnaires, and structured interviews for IEI, depression, anxiety, and SFD.
Results: More than half of the IEI subjects met Diagnostic and Statistical Manual of Mental Disorders, fourth edition criteria of SFD. This group shared both symptoms and psychological features of somatization with the SFD group. IEI subjects who did not fulfill criteria for a specific SFD were less impaired by their chemical sensitivity but differed nevertheless from nonsomatoform controls by significantly higher symptom scores, higher trait anxiety, a focus on autonomic sensations, and more pronounced somatic symptom attributions. These psychological features were significantly associated with the burden of somatic symptoms in both SFD and IEI. Furthermore, self-reported allergy but not total immunoglobulin E correlated with symptom burden in the total sample.
Conclusions: The similarity of IEI and SFD regarding symptoms and psychological features of somatization support the hypothesis that IEI is a variant of SFD.
Key Words: idiopathic environmental intolerance • multiple chemical sensitivity • SFDs • perceptual style • symptom attribution • medically unexplained symptoms
Abbreviations: IEI = idiopathic environmental intolerance; SFD = somatoform disorder; ESQ = Environmental Sensitivity Questionnaire; DSM-IV = Diagnostic and Statistical Manual of Mental Disorders, fourth edition; ANOVA = analysis of variance; SIQ = Symptom Interpretation Questionnaire; PHQ-9 = Patient Health Questionnaire depressive symptom severity scale; PHQ-15 = Patient Health Questionnaire somatic symptom severity scale; SOMS = screening for somatoform symptoms; STAI = State Trait Anxiety Inventory; COSS = Chemical Odor Sensitivity Scale; SCID = Structured Clinical Interview for DSM-IV; ACQ = Agoraphobic Cognition Questionnaire; CABAH = Cognitions about Body and Health Questionnaire.
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INTRODUCTION |
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The IEI syndrome is characterized by multiple affective, cognitive, and somatic complaints. Common symptoms include headache, fatigue, joint pain, muscle pain, nervousness, sleep problems, burning of the eyes, nausea, dizziness, weakness, memory problems, gastrointestinal symptoms, and respiratory symptoms (14–16). Typical IEI patients in clinical studies are middle-aged, well-educated females. Women represent 60 to 80% of the study samples. The average age is in the fourth decade (15,17,18). Psychiatric comorbidity among IEI patients is very high, ranging from 42 to 100% (18). In the largest clinical sample investigated to date with structured clinical interviews for DSM-IV (SCID), 66% of the 295 IEI patients met criteria for at least one current Diagnostic and Statistical Manual of Mental Disorders, fourth edition (DSM-IV) diagnosis (15). The most common diagnosis was somatoform disorder (SFD), followed by affective and anxiety disorder.
There is no universally accepted theory regarding the etiology and pathogenesis of IEI. Toxicogenic, psychogenic, and interactive theories have been proposed (3). Some authors assume that IEI is a primarily physical or toxic reaction to environmental chemical exposures; others favor behavioral, emotional, and cognitive causal mechanisms (3).
It has also been suggested that IEI is simply a variant of SFDs or the so-called "functional somatic syndromes" and that somatization may be the common ground of all these syndromes (19–22). We found some empirical evidence for this assumption in previous studies by comparing IEI with non-IEI subjects (5,21,22). The aim of the present study was to replicate these findings by using a more sophisticated methodology, a better characterized IEI sample, and a second control group of somatoform subjects to allow a direct comparison of IEI and SFD. Our expectation is that IEI and SFD individuals share central characteristics and cannot be distinguished on the phenomenological level except with regard to different styles of symptom attribution. This hypothesis was tested by comparing a clinical and a subclinical IEI group with a somatoform and a nonsomatoform control group, both free from IEI, using standardized symptom scales, psychological questionnaires, and structured interviews for IEI, depression, anxiety, and SFDs. If IEI is indeed a variant of SFDs, IEI and non-IEI somatoform subjects should overlap not only in symptoms but also in those psychological attributes typically found in somatizing patients (e.g., trait negative affectivity, specific cognitive styles such as heightened vigilance toward bodily sensations and a self-concept of bodily weakness (23–25), and somatic attributions of symptoms (26)). Also, correlational patterns between these psychological attributes and self-reported somatic symptoms should be similar in IEI and SFD individuals. We controlled for self-reported allergic diseases because allergies and asthma are often reported to be associated with chemical sensitivity (8,9,22,27).
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METHODS |
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General exclusion criteria were age below 18 and above 65 years, organic brain disease, present or past psychotic disorder, presence of a somatic disease that could account for the reported bodily complaints, and disorders associated with substance use. Those who completed the entire study were paid 60 Euro. All subjects provided written informed consent.
The subjects were recruited from several sources. IEI and somatoform subjects were recruited from polyclinics of environmental medicine, psychiatry, and psychosomatic medicine at the University of Heidelberg (Germany) and by different advertisements in local newspapers asking for volunteers who were either especially sensitive to environmental chemicals or suffering from medically unexplained physical symptoms. The control subjects were recruited from a polyclinic of dental medicine (mainly patients who attend to the polyclinic for routine check-ups but not for complaints that could be suspected to be somatoform), by advertisements in local newspapers, and from health centers asking for participation in an environmental health study.
IEI Case Definition
Subjects who met the following 3 criteria were given the diagnosis of IEI: a) presence of at least 3 symptoms, each lasting at least 6 months; b) naming at least 3 trigger substances that mostly or always provoke symptoms; and c) avoiding at least 3 trigger substances mostly or always. Our case definition is similar to those used by Black et al. (6) and Nimnuan et al. (11), with an additional criterion for chronicity to identify more severe IEI cases. These criteria were checked in a fully structured interview (unpublished) with 2 sections. Section 1 covered 15 characteristic trigger substances (car exhaust, perfumes, pesticide, cleansing agents, cigarette smoke, new clothes, new furniture, new carpeting, paints, electric appliance, hair spray, varnish, gas, amalgam fillings, and air pollution). Section 2 covered 15 symptoms linked to environmental chemicals (dry nose, smell sensitivity, muscle or joint pains, skin problems, poor concentration, memory problems, headache, fatigue, nervousness, dry mouth, palpitation, nausea, breathing difficulties, burning eyes, and abdominal pain). The subjects were asked how often (0 = never, 4 = always) exposure to each substance provokes symptoms and how often (0 = never, 4 = always) they avoid that particular substance. For each criterion a composite score was formed by adding up a) the number of symptoms with a duration of at least 6 months (Cronbach’s 
= 0.87), b) the number of trigger substances that mostly or always provoked symptoms (Cronbach’s = 0.91), and c) the number of substances mostly or always avoided by the subject (Cronbach’s = 0.91).
Sample
At stage 2 of the subject recruitment, 174 positively or negatively screened subjects were evaluated with a psychiatric interview (SCID, 31), and a second structured interview to reach the criteria-based IEI diagnosis described above. After this evaluation, 5 subjects met our exclusion criteria (1 subject had a psychotic disorder, 3 others a substance use associated disorder, and one did not comply), and 3 did not meet the inclusion criteria. In a final step, we excluded 6 subjects from the IEI group because they did not meet all interview-based IEI criteria (false screening positives), and 8 subjects from the 2 control groups (6 SFD and 2 CG subjects) who were diagnosed in the interview as IEI (false screening negatives).
Comparison Groups
To decide whether IEI subjects can be distinguished from somatoform and nonsomatoform individuals without IEI, we defined the following 4 comparison groups: of the 54 IEI subjects, 23 fulfilled only the interview-based criteria of IEI but did not reach the full criteria for a specific SFD in the SCID, thus called "IEI only." The remaining 31 IEI individuals fulfilled both interview-based criteria of IEI and criteria of a specific somatoform disorder (SFD), thus called "IEI&SFD". A first control group consisted of 44 subjects who met DSM-IV criteria of a SFD but not the interview-based criteria of IEI, thus called "SFD only." A second control group of 54 subjects was free of both SFD and IEI diagnosis, thus called "nonsomatoform CG."
Measures
Structured Clinical Interviews
The SCID I (31) was used to assess diagnoses of somatoform and of current affective and anxiety disorders according to DSM-IV. If criteria were met for more than one disorder, all of them were diagnosed, including also dual diagnoses consisting of a somatoform and a non-SFD. The SCID interview included an additional section (from Diagnostic Interview for Mental Disorders (32)) for conversion disorders. The criteria for all types of SFDs were checked at least once except the unspecified category "SFD not otherwise specified." The SCID is a valid and reliable semi-structured interview guide. Trained clinical psychologists (2 PhD psychology candidates) administered the SCID and also the fully structured IEI interview. All interviewers had received 1 full week of training by a SCID expert and were afterward closely supervised by one of the senior researchers (J.B.) who had extensive psychiatric and psychosomatic clinical experience. The interviewers were encouraged to use all available sources of information (patient, laboratory findings, former medical diagnoses, and medical records) to evaluate the presence or absence of a symptom. Interrater reliabilities of the 2 diagnostic instruments were derived from 30 subjects (10 of each group), evaluated by a rater and a co-rater in a conjoint interview. Intraclass correlation coefficients between raters 1 and 2 were as follows: r = .99 for the IEI trigger substances, r = .99 for the IEI symptoms, and r = .99 for IEI avoidance behavior. 
coefficients were 0.92 for the IEI diagnosis, 1.00 for the category "any SFD" (range for single diagnoses, 0.78–1.00), 0.83 for "any current anxiety disorders" (range, 0.65–1.00), and 1.00 for "any current depression." The high coefficients result from the use of conjoint interviews.
Medical Evaluation
All subjects from all groups underwent a standardized medical examination by a dermatologist. Allergic diseases were documented in standardized form in an extensive questionnaire. Blood samples were drawn for routine biochemical tests, and immunoglobulin E (total IgE) antibodies in the serum were determined as a general indicator of an atopic predisposition and objective screening of allergies. Skin prick tests could not be performed because of limited financial research resources. This medical examination took place in a polyclinic of environmental medicine; the diagnostic interviews were conducted later at the same place.
Self-Report Measures
Environmental Sensitivity
The Chemical Odor Sensitivity Scale (COSS, 5) contains 11 statements describing strong physical responses (trouble in breathing, nausea, cough, and dizziness) to the odor of common environmental chemicals (sprays, paints, cigarette smoke, cleansing agents, perfumes, exhaust fumes, and gasoline). Unidimensionality, reliability and validity of the COSS have been demonstrated (5,22). The General Environmental Sensitivity Scale (GESS, 5) assesses general sensitivity to a range of environmental stimuli (noise, taste, cold, and loud colors). This 5-item scale showed adequate internal consistency across diverse samples (5). The Environmental Sensitivity Questionnaire (ESQ) is a 10-item self-report questionnaire designed to measure cognitions of environmental threat. Subjects are asked to evaluate a number of environmental substances for their damaging effect on their health. The list of substances presented includes diverse dental materials (amalgam, gold, composite, and palladium) and various environmental agents (electro smog, passive cigarette smoking, radioactivity from nuclear reactors, and chemicals or other potentially harmful substances in the air, in the water, and in the food). The scale was found to be of good reliability and validity (21,22,33).
Symptom Scales
The PHQ-15 is a valid and reliable measure of somatic symptom severity and comprises 15 somatic symptoms from the (PHQ, 28). The PHQ-15 covers the most prevalent DSM-IV somatization disorder symptoms. The subjects are asked to rate the severity of each symptom from 0 ("not bothered at all") to 2 ("bothered a lot"). The total score ranges from 0 to 30 (30). The PHQ-9 is the depressive symptom severity scale from the PHQ, consisting of 9 items (30). The Screening for Somatoform Symptoms (SOMS, 34) consists of 53 somatic symptoms relevant for the diagnosis of somatization disorder according to DSM-IV and ICD-10. Subjects had to mark all those symptoms present during the last 2 years, which caused suffering but could not be attributed to a medical cause by a physician. Reported symptoms were added to yield a symptom total score and 4 subscores. Retest reliability and validity have been shown for the SOMS symptom scores (34,35). The Freiburg Complaint List-Revised (FBL-R, (36)) is a reliable self-report questionnaire that lists 80 somatic complaints. We used the symptom total score only. The SCL-90R is a well-validated self-report scale that asks for the presence and severity of 90 somatic and mental symptoms during the previous 7 days (29). In this study the somatization subscale and global severity index were used.
Risk Factors for Somatization
The German version of the State-Trait Anxiety Inventory (STAI) was used to assess trait negative affectivity (37) and the Agoraphobic Cognition Questionnaire (ACQ (38)) was used to assess catastrophizing thoughts related to bodily symptoms. According to the authors the 14 items of the ACQ can be subdivided into 2 subscales with 7 items each: (subscale 1) "loss of control" (typical in agoraphobia) and (subscale 2) "physical concerns" (typical in panic or SFDs). The Cognitions About Body and Health Questionnaire (CABAH) assesses cognitive styles, attitudes, and interpretations of body perceptions typically found in patients with SFDs (25). This 31-item questionnaire consists of 5 scales: Catastrophizing Interpretation of Bodily Complaints, Autonomic Sensations, Bodily Weakness, Intolerance to Bodily Complaints, and Health Habits. The CABAH scales were demonstrated to be reliable and valid (25). The Symptom Interpretation Questionnaire (SIQ, 26) is a widely used self-report measure examining causal attributions for 13 common somatic symptoms (such as lost of appetite and feeling dizzy). Respondents are asked how much they attribute each symptom to (a) physical illness, (b) emotional distress, and (c) normal environmental causes. It yields 3 scores, representing somatic, psychological, and normalizing or external attributions. All scales of our German version of the SIQ have good internal reliability.
Data Analysis
Groups were compared using series of analyses of variance (ANOVAs) for continuous variables, and 
2 tests for categorical data. Spearman correlation coefficients were used to examine correlations between continuous variables within the diagnostic groups. A hierarchical multiple regression was performed to determine the proportion of variance in somatic symptoms explained by a set of potential predictors. Two-tailed p values are presented throughout. Bonferroni corrections were applied to multiple comparisons. All statistical analyses were performed with SPSS Version 11.5 for MS Windows.
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RESULTS |
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Psychological Symptoms and Bodily Complaints
A series of ANOVAs was conducted to compare the 4 diagnostic groups on several symptom scales assessing somatic symptom severity, depression, and general psychological impairment (Table 2). As expected, all 3 groups with functional somatic syndromes had significantly higher symptom scores on nearly all scales than the nonsomatoform CG. Again, the IEI only group had significantly elevated somatic symptom scores compared with the CG but lower scores on 3 of the 4 somatic symptom measures than the 2 SFD groups.
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Frequency of Somatoform, Depressive, and Anxiety Disorders
The prevalence of DSM-IV diagnoses (39) in each of the 4 groups is summarized in Table 3. The CG did not differ from the IEI only group with regard to the number of DSM-IV diagnoses. The IEI&SFD group was characterized by the highest rate of an additional current depression, and the SFD showed the highest prevalence of an additional current anxiety disorder.
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Trait Anxiety, Body-Related Cognitions, and Symptom Attribution
Table 4 summarizes group differences on psychological scales measuring risk factors for somatization. ANOVAs revealed significant group differences on 7 of the 11 measures with post hoc tests indicating significantly higher scores for the 3 groups with functional somatic syndromes on trait anxiety, autonomic sensations, and somatic symptom attributions compared with nonsomatoform controls. Additionally, both IEI&SFD and SFD only subjects felt bodily weaker and reported more physical concerns than CG subjects. Most important, IEI&SFD and SFD only subjects did not differ on any of the 11 measures except for neutralizing symptom attributions. IEI subjects made more neutralizing or environmental symptom attributions than non-IEI subjects, but this difference reached significance only for the IEI&SFD group.
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Self-Reported Allergy and Total-IgE Values
Significantly more subjects with IEI reported allergies (IEI, 78.3%; IEI&SFD, 80.6%), such as skin or food allergies, allergic diseases of the lung and bronchi, and allergic rhinitis, than SFD (63.6%) and CG (37%) subjects (2 = 20.8, df = 3, p < .001). However, the groups did not differ significantly with regard to objective measures of allergic diseases, such as the total-IgE antibody concentration (Kruskal Wallis test, 2 = 1.76; p = .62) or the proportion of subjects with elevated total-IgE values (>120 kU/l), which varied in the present study sample between 17.4% (IEI), 20.4% (CG), 20.5% (SFD), and 22.6% (IEI&SFD) (2 = 0.22, df = 3, p = .974).
Correlations Between Risk Factors and Somatic Complaints
The last set of analyses examined whether the correlation patterns between psychological and biological risk factors and somatic complaints were similar among IEI and SFD subjects (Table 5). The 2 IEI groups were combined for these analyses to enhance sample size. According to these analyses, those psychological variables discriminating somatoform from nonsomatoform subjects were also significantly correlated with the number of somatoform symptoms, not only in the total sample but also in the IEI and the SFD group. In the total sample, self-reported allergy was significantly associated with somatic symptoms but not total-IgE. Finally, a hierarchical multiple regression analysis was conducted to identify the strongest predictors of functional somatic symptoms in the total sample. The 7 psychological predictors entered into the regression model after controlling for the 2 biological predictors (self-reported allergy and IgE) raised R2 from 0.13 (explained by the biological variables) to 0.59. According to the standardized ß coefficients of the final model presented in Table 5, trait anxiety was the strongest predictor followed by somatic attributions, bodily weakness, and self-reported allergy.
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DISCUSSION |
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SFD was the most frequent diagnosis among IEI individuals: 57% of the IEI subjects met the DSM-IV criteria for a least one specific disorder from this diagnostic category, predominantly somatization disorder (35%), and undifferentiated SFD (17%). But the coexistence of IEI and SFD does not imply that the IEI&SFD subjects in fact had 2 discrete disorders, because the medically unexplained symptoms attributed by the individuals to environmental chemicals were counted, in the SCID interview, as symptoms contributing to a SFD diagnosis. Therefore, the high prevalence of SFD among IEI subjects mainly result from overlapping diagnostic criteria for IEI and SFD diagnosis. Differences in selection processes, diagnostic criteria for IEI, and exclusion criteria may be responsible for the lower prevalence rate of SFD (37%) recently reported for a large clinic sample of IEI patients (15).
Subdividing the IEI group by taking into account who fulfilled SFD criteria and who did not, it became obvious that IEI subjects who met full SFD criteria suffered from a more severe type of IEI, reporting more bodily complaints and more doctor visits than the IEI subjects who failed to meet full criteria of a SFD. However, the IEI only group, although less impaired by their chemical sensitivity, differed from the CG on nearly all symptom scales by significantly higher scores. Thus they represent a moderate type of SFD, characterized by multiple unexplained complaints lasting at least 6 months but below the threshold for a diagnosis of a particular SFD. The reason why these subjects were not classified as undifferentiated SFD was that their complaints did not cause clinically significant distress or significant impairment in social, occupational, or other important areas of functioning.
Still, the mean number of unexplained physical symptoms reported by the IEI only group in the SOMS was 3 times as high as the base rate found in a representative general population sample in Germany (40). As in previous studies (17,18), the IEI individuals also had significantly higher depression and anxiety scores than the nonsomatoform controls, but the severe IEI and the SFD groups did not differ, neither in symptoms nor on the diagnosis level.
With respect to the psychological risk factors assessed via self-report scales, the 3 somatoform groups had significantly enhanced trait anxiety, physical concerns, and dysfunctional body-related cognitions, and they made more somatic symptom attributions than the nonsomatoform group. The more severe IEI cases did not differ from the subjects of the SFD group on any of these scales, except by enhanced normalizing attributions scale of the SIQ. However, this style was quite in line with their diagnosis: IEI subjects preferably explained common somatic complaints by external or environmental events (e.g., loud noise, bright light, too much coffee, air pollution, and unsuitable food). According to the correlational analyses, the hypothesized risk factors for somatization and self-reported somatic symptoms are strongly associated: measures of trait negative affectivity and specific cognitive styles, such as heightened vigilance toward bodily sensations and a self-concept of bodily weakness, were significantly related to functional somatic symptoms in both SFD and IEI subjects. In the IEI groups, most of these variables were also correlated to the number of self-reported IEI symptoms.
Self-reported allergic diseases were common among IEI and SFD subjects and were a further important predictor of somatic symptoms. However, we cannot decide if this association was because of organic reasons, reflects simply a reporting bias of people overly involved with bodily symptoms, or is caused by a third factor (genetic or environmental). But the diagnostic groups did not differ in IgE, our only objective measure to validate the self-report of allergic disease and, more importantly, IgE was not correlated with the somatic symptom burden. When self-reported allergy and IgE were entered together with psychological variables into a multiple regression analysis to predict symptom burden, trait anxiety was the strongest predictor, followed by somatic attributions, bodily weakness, and self-reported allergy. Thus, objective illness indicators did predict less symptoms than psychological risk factors.
Despite the limitations of our study, it is tempting to integrate the results in a hypothetical cognitive-behavioral model of IEI. We assume that subjective odor mediated hypersensitivity toward common chemical agents is an enduring personality characteristic that predisposes people to develop an environment-related functional somatic syndrome called IEI. The clinical IEI syndrome may arise from the interaction between this specific predisposition and environmental stress (e.g., psychogenic traumata, critical life events, daily life problems, and hassles), physiological changes caused by an organic disease (e.g., asthma or allergy), beliefs about the harm of environmental chemicals (induced via information from mass media, support groups, family members, and medical specialists or acquired by associative learning), and the existence of additional vulnerability traits such as negative affectivity, suggestibility, or a self-concept of bodily weakness. The maintenance of the syndrome is largely determined by a self-perpetuating cycle of increased attention to environmental exposure and bodily sensations that turns into biased symptom perception and further amplification of bodily complaints, which then may be misinterpreted as symptoms of IEI. The results of the present report are in accordance with this speculative model.
Besides the drawbacks of a cross-sectional study, further methodological limitations of the study should be pointed out. First, the generalization of results is limited by the sampling procedure, the inclusion and exclusion criteria, and the case criteria used to define IEI. The majority of the subjects assigned to the diagnostic groups were recruited by advertisements (CG, 76%; IEI, 78%; SFD, 66%), the remaining subjects stem from various polyclinics and primary care practices. The subjects obtained neither treatment nor a detailed diagnostic feedback from the research staff; therefore, neither the IEI nor the SFD subjects are completely comparable to typical IEI or somatoform patients. However, the demographic and psychopathological features of both the IEI and the SFD subjects were similar to those found in patients with help-seeking behavior (14,15,35,41). Nevertheless, our recruitment procedure might have favored polysmptomatic subjects but free of additional depressive disorders in both somatoform groups. Second, an additional control group with a chronic illness of clearly organic origin would have allowed us to test if the psychological abnormalities we found in IEIs simply represent a reaction to severe illness and not to somatization per se. This is to be considered even more, because allergic diseases were reported by a large part of IEI and SFD participants. Therefore at least part of the self-reported complaints might be explained by a medical condition. The medical examination by our research dermatologist was not sufficient to rule out a medical condition for each of the reported symptoms. Therefore, those critical symptoms that the subjects have attributed to a self-reported definitive illness were either not counted as somatoform or the interviewers followed the DSM-IV C2 criterion for the diagnosis of SFD, which asks for complaints and impairments in excess of what can be expected from a present organic condition. In the absence of a chronic illness comparison group, we have to rely on this aspect of the diagnosis to reduce the impact of allergic diseases on the resulting diagnosis. Third, the SCID and the IEI interviews were administered by trained interviewers who nonetheless had limited clinical expertise. Their symptom ratings relied primarily on self-report without consistent validation using secondary sources or medical records. Therefore, it is possible that some physical symptoms were falsely classified. A recently published chart review method (42) could enhance both the validity of somatoform SCID diagnoses and of data about medical comorbidities in future studies. A final issue is our IEI definition. At present, there are no universally accepted standardized measures for IEI case identification and definition. Hence, we used a validated screening questionnaire (5) to identify potential cases, followed by a fully structured interview to check our operationally defined case criteria. These criteria refer to the IEI concept and are similar to those used by Black et al. (6) and Nimnuan et al. (11), but they are not equivalent to the very restrictive case criteria originally proposed by Cullen (43). This highly controversial case definition leads to an extreme selection bias toward a chemical causation model, because it requires an initial triggering event (i.e., exposure to a toxic agent) and the reliable elicitation of symptoms through exposure. Until causation of IEI is clarified, we prefer to use diagnostic concepts free from etiological assumptions. We also recommend not excluding people with preexistent or concurrent organic diseases (e.g., asthma, allergy, or arthritis) or mental disorders (e.g., depression and anxiety disorders) as long as these conditions do not fully explain the subjective complaints attributed to chemical exposure.
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NOTES |
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Supported by a grant (BA-1597-3) from the Deutsche Forschungsgemein schaft.
DOI:10.1097/01.psy.0000174170.66109.b7
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REFERENCES |
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ngste, Kognitionen und Vermeidung (AKV) [The Body Sensations Questionnaire and the Agoraphobic Cognitions Questionnaire.–Manual of the German version]. Weinheim, Germany, Beltz Publishers; 1993.
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