Personality, mental distress, and subjective health ... - SAGE Journals

Human & Experimental Toxicology (2007) 26: 231 241 http://het.sagepub.com

Personality, mental distress, and subjective health complaints among persons with environmental annoyance ¨ sterberg1, R Persson2, B Karlson1, F Carlsson Eek1 and P Ørbæk2 K O 1

Department of Laboratory Medicine, Division of Occupational and Environmental Medicine, Lund University, Sweden; National Institute of Occupational Health, Copenhagen, Denmark

2

The aim of this study was to assess possible early determinants of idiopathic environmental intolerance (IEI), contributing to an integrated model for the development of IEI. Questionnaires concerning personality traits, current mental distress, subjective health complaints, work load and satisfaction, and options for recovery, were given to 84 persons from the general population attributing annoyance to (i) chemicals/smells (smell-annoyed (SA) n /29); (ii) electrical equipment (electrically annoyed (EA) n /16); and (iii) both smells and electricity (generally annoyed (GA) n /39), but otherwise healthy and in active work. Compared to referents (n /54), the EA and GA groups showed strongly elevated scores on 5/6 scales within the trait anxiety/ neuroticism personality dimension, while the SA group had a slight elevation on only one anxiety scale. Current

mental distress and subjective health complaints scores were generally elevated in the EA and GA groups, but only partially in the SA group. Higher proportions of the EA, GA, and SA groups reported low satisfaction with their work situation, including more frequent fatigue after work and a higher, and often unfulfilled, need for recovery. The findings suggest that trait anxiety is prominent already at prodromal stages of IEI, possibly indicating that trait anxiety facilitates the acquisition of attribution of health complaints to environmental factors. Human & Experimental Toxicology (2007) 26, 231 241 Key words: electrical hypersensitivity; idiopathic environmental intolerance; multiple chemical sensitivity

Introduction During recent decades, annoyance reactions relating to everyday environmental exposures, such as indoor air climate, chemical scents and electromagnetic fields, have received increasing attention.1,2 These ‘medically unexplained’ conditions have, in common, unspecific complaints, such as fatigue, pain, nausea, and gastrointestinal problems, and a disability out of proportion to the results of physical examinations and laboratory tests.3 Controlled, experimental, exposure studies of patients have not shown any relationship between symptoms and the neurotoxicity of the chemicals exposed to, or the presence of electromagnetic fields, but symptoms have shown a relationship with perceptual characteristics, such as odor intensity or the proximity to ¨ sterberg, PhD, Department of Occupa*Correspondence: Kai O tional and Environmental Medicine, Lund University Hospital, SE-22185 Lund, Sweden E-mail: [email protected] Received 31 October 2005; revised 20 March 2006; accepted 3 April 2006

– 2007 SAGE Publications

electrical equipment, and with a belief of ongoing noxious exposure to, for example, electromagnetic fields.4,5 At a WHO workshop held in 1996, it was concluded that medically unexplained disorders associated with environmental factors should be regarded as one single category, idiopathic environmental intolerance (IEI).6 This concept has empirical support by the considerable overlap of nonspecific health complaints found across allegedly ‘specific’ syndromes (eg, multiple chemical sensitivity’ and ‘electrical hypersensitivity), and by the fact that many patients attribute health complaints to several environmental factors, such as chemicals, electrical equipment, foods, air climate, etc.2,3,7 10 Recent population surveys have indicated that milder forms of IEI are surprisingly common, encompassing some 15 30% of the population.11,12 At the same time, the present understanding of IEI rests heavily on studies of clinical patients, which makes it problematic to generalize the findings to the milder or ‘subclinical’ forms of IEI, which are seemingly common in the population. A number of 10.1177/0960327107070575

Personality and environmental annoyance ¨ sterberg et al. K. O

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studies of clinical multiple chemical sensitivity patients have indicated the presence of current mental distress in standardized self-report questionnaires, most commonly shown by elevations on the Somatization and Depression subscales of the Symptom Checklist-90.13 17 Moreover, the use of various self-rating questionnaires, intended to measure stable personality patterns (ie, personality traits), has shown that certain traits are more pronounced among patients with multiple chemical sensitivity (MCS); mainly anxiety,17 19 and depression.18,19 However, it has not yet been possible to exclude the possibility that such indications of emotional imbalance reflect secondary reactions to disablement, which has been demonstrated among clinical patients suffering from a well-defined somatic disease, such as arthritis.20 For example, concerning ‘chronic fatigue syndrome (CFS), a study of a community sample showed less dysfunction and less psychiatric morbidity than that found among clinical CFS patients.21 One study of fibromyalgia patients showed that psychiatric diagnoses were related to the health care seeking behavior of patients rather than fibromyalgia per se .22 It has, thus, remained unclear whether the mental distress and personality traits observed among clinical IEI patients represent a constitutional vulnerability which is a prerequisite for developing IEI, or merely reflect secondary reactions, characterizing the ‘sickrole’ often entered into after several years of seeking health care and attempting various forms of treatment. In order to gain a better understanding of the role of personality traits and current mental distress in the attribution of health complaints to environmental factors, it might be more appropriate to study these dimensions among non-patients who have not actively sought health care for their environmental sensitivity. Such non-patients can be assumed to have less handicapping sensitivity reactions, which might, hypothetically, represent a prodromal stage to IEI. Since it is unlikely that such non-patients have entered into a sick-role or disablement that might affect the reporting on questions regarding personality and emotional symptoms, the findings in personality tests in this group might provide an insight into the very early determinants to IEI, which, to our knowledge, has not been studied before. This study presents data from an examination of occupationally-active non-patients, recruited from the general population, reporting subjective annoyance to ambient smells or electromagnetic equipment, but being, otherwise, healthy and wellfunctioning. The objectives were to determine whether these persons would show (i) a specific

pattern of personality traits; (ii) a higher level of general health complaints; (iii) whether they perceived their situation at work in more negative terms; and (iv) perceived less satisfactory recovery. The study aimed to supplement our previous findings in these groups of persons during chemical odor provocation,23 and daily life monitoring of stress, health complaints, and avoidance behaviors (Persson et al ., unpublished observations), and endocrine manipulation.24 The overall purpose of this research program was to provide information about possible early determinants of IEI and to assess whether the findings would fit into an integrated model for explaining the development of IEI.

Methods Participants The target group comprised persons having reported annoyance attributed to electrical equipment or ambient odors in their everyday life, but were otherwise healthy. The participants were identified among the repliers (n /13381) to a population survey concerning illness prevalence and health care consumption in the southernmost county of Sweden, Ska˚ne (Scania), which had been carried out a few years prior to the present study.25 The inventory used in the population survey contained five questions concerning annoyance attributed to smells and electrical equipment. The presence of environmental annoyance was defined as scoring on the highest level (‘much annoyed’; score 2 on the scale 0 2) on at least one of the five questions about perceived annoyance from exposure to electrical equipment (three questions) and odors (two questions) during the past 2 weeks. Persons having reported long-term sick leave or disability pension in the initial questionnaire, or exceeding 58 years of age, were not invited, in order to minimize the number of participants having chronic illness or approaching retirement. As a further precaution, the written invitation dissuaded participation in case of serious illness or long-term medication (eg, diabetes, arthritis, asthma, severe allergy, or psychiatric disorder). By these criteria, a sample of 315 eligible participants was identified, of which 118 persons agreed to participate, and 84 finally completed all parts of the study. Detailed selection criteria, procedures, and subject-related data have been described in detail in previous publications of other parts of the study.23 Persons reporting high annoyance attributed to both types of exposure (ie, electricity and odors) were classified as generally annoyed (GA; n /39), while those reporting annoyance attributed


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to only one of the exposure types were classified as either electrically annoyed (EA; n /16) or smell annoyed (SA; n/29), respectively. To validate the long-standing nature of environmental annoyance, a modified version of the Questionnaire on Chemical and General Environmental Sensitivity (CGES)26 was included in the present set of inventories, showing expected higher scores in the EA, SA and GA groups compared to referents, although only a minority within each group reached the criterion of ‘MCS’ or ‘electrical sensitivity’.23 The reference group consisted of a sample of repliers to the population study inventory, having disavowed any annoyance attributed to electrical equipment or odors on all five questions. The reference sample was compiled with respect to age, gender, and socioeconomic status, in order to create a demographic distribution comparable to that in the annoyance groups, but was, in other respects, selected at random. The same final sample of 54 referents, as included in the chemical odor provocation study,23 was used, providing an age and gender distribution close to even across all groups; 53% were female, and mean age was 43.5 years (SD: 9.1) among EA/SA/GA subjects, and 43.7 years (SD: 9.6) among referents. As a final precaution, all participants underwent a comprehensive medical work-up to secure the absence of any significant disease. Inventories The Swedish Universities Scales of Personality (SSP) was used to assess personality traits.27 SSP is a revised version of the Karolinska Scales of Personality (KSP),28 which has been extensively used in international personality research since 1979.27 SSP consists of 91 items, divided into 13 seven-item scales, each covering one personality dimension (Table 1). Each item is given as a statement and answered on a four-point scale (1 4), ranging from ‘does not apply at all’ to ‘applies completely’. The 13 scales are grouped into three main personality dimensions according to a threefactor solution: neuroticism, aggressiveness, and extraversion. The three-factor structure of the SSP corresponds to well-known personality theories, particularly the model behind the frequently used Eysenck Personality Inventory (EPI).29 The SSP dimensions of neuroticism and extraversion is similar to the EPI dimensions with the same labels, and the ‘aggressiveness’ dimension has some overlap with the ‘psychoticism’ factor of the EPI. The Symptom Checklist-35 (SCL-35) was used to assess current mental distress, defined as psychological symptoms present ‘during the last seven days including today’. The SCL-35 is an abbreviated

13

version of the Symptom Checklist-90, a widelyused standardized inventory, with 90 items that are rated on a five-point distress scale (0 4), with labels ranging from ‘not at all’ to ‘extremely’, comprising nine main symptom scales. The brief SCL-35 included the 35 items of the scales somatization (12 items), depression (13 items), and anxiety (10 items). In addition, the subject’s mean score across all 35 items, the Global Severity Index (GSI), was analysed. The Lund Subjective Health Complaints (LSHC) inventory, developed at the Department of Occupational and Environmental Medicine at the University Hospital in Lund, was used to assess common health complaints. The LSHC is similar to the Ursin Health Inventory/Subjective Health Complaints scale,30 and addresses the frequency of common health complaints during the preceding 30 days. The 29 items are responded to on a five-point scale, reflecting how frequent a symptom has been encountered during the last 30 days: (0) ‘never’, (1) ‘rarely (a few times)’, (2) ‘sometimes (once or twice a week)’, (3) ‘most of the time (a couple of times a week)’, and (4) ‘always (every day, more or less)’. Items were categorized based on a previous factor analysis, carried out on data from a larger population sample (Karlson, unpublished observations), resulting in an eight-factor solution providing the subscales: asthenia/depression (seven items), pain (four items), gastrointestinal complaints (four items), heart and respiratory complaints (three items), loss of appetite (two items), headache/migraine (two items), constipation/heat flushes (two items), and ‘other complaints’ (five items; mental exhaustion, dizziness, skin rash, sleeping problems, flu-like symptoms). Work load and recovery was assessed by a questionnaire compiled from items used in previous studies and items from the General Nordic Questionnaire for Psychological and Social Factors at Work (QPS-Nordic).31 It contained: (a) 10 items concerning factual data, such as length and type of employment, working hours, and amount of overtime; (b) 10 items concerning work satisfaction, eg, concerning present work hours, tasks, and personal performance (including QPS items No. 66 69); (c) five items concerning interaction with fellow workers, and presence and extent of harassment or bullying at the workplace (QPS items No. 81 83); and (d) 11 items about work-related fatigue, quality of sleep, and recovery requirements. Questions were answered on a five-point Likert scale, except for questions asking for a yes/no reply (eg, harassment, shift work, job on the side) and continuous numerical data (eg, length of employment, working hours).


*Gender and age were included in the ANOVA model where appropriate, and P -values have been adjusted accordingly; h2p, partial eta squared. a Subscale with negative loading.

0.02 0.05 0.01 0.452 0.102 0.820 0.42 0.41 0.41 2.18 2.28 2.15 0.54 0.54 0.42 2.23 2.42 2.23 0.51 0.56 0.52 0.59 0.51 0.47 2.41 2.63 2.25

2.26 2.35 2.22

0.01 0.04 0.01 0.01 0.729 0.188 0.572 0.608 0.38 0.52 0.53 0.58 2.74 2.14 1.99 1.83 0.28 0.48 0.49 0.59 2.66 2.35 2.08 1.90 0.36 0.49 0.59 0.61 0.32 0.80 0.62 0.52 2.69 2.36 1.94 1.83

2.73 2.17 2.12 1.98

B/0.001 0.002 0.001 B/0.001 0.001 0.456 0.052 0.830 0.182 0.117 B/0.001 B/0.001 0.008 0.010 0.012 0.25 0.13 0.11 0.02 0.13 0.09 B/0.001 B/0.001 0.002 0.367 B/0.001 0.005 0.43 0.45 0.43 0.44 0.40 0.46 1.55 1.61 1.83 1.90 1.49 1.69 0.64 0.59 0.61 0.49 0.57 0.54 2.09 1.99 2.19 1.98 1.93 2.04 0.39 0.58 0.49 0.48 0.43 0.49 1.65 1.86 1.87 2.07 1.64 1.88 0.69 0.72 0.49 0.65 0.63 0.61

P SD M SD M SD SD

2.28 2.18 2.20 2.08 1.86 2.06

Neuroticism Somatic trait anxiety Psychic trait anxiety Stress susceptibility Lack of assertiveness Embitterment Mistrust Aggressiveness Social desirabilitya Trait irritability Verbal trait aggression Physical trait aggression Extraversion Impulsiveness Adventure seeking Detachmenta

GA versus Ref. P SA versus Ref. P h2p

EA versus Ref. P

Post-hoc t -test ANOVA* group Referents (n/54) GA (n/39)

M

Swedish Universities Scales of Personality (SSP) ANOVA group differences were found exclusively on the scales within the neuroticism dimension (Table 1), namely somatic trait anxiety (P B/0.001; h2p /0.25), psychic trait anxiety (P B/0.001; h2p / 0.13), stress susceptibility P /0.002; h2p /0.11), embitterment (P B/0.001; h2p /0.13), and mistrust (P / 0.005; h2p /0.09). Post hoc analyses showed that the EA and GA groups shared a similar profile of strongly elevated scores on all these scales compared to the referents (post-hoc P 5/0.01), while the only deviation observed for the SA group was a

M

Results

SA (n/29)

Ethics All subjects gave written informed consent to participate in the study, and the study protocol was approved by the Ethics Committee of Lund University (LU 343-00; LU 147-01).

EA (n/16)

Statistical analysis The statistical software SPSS for Windows 12.0 was used for all analyses. Due to skewed distributions, the scale scores of the SCL-35 were ranked before analysis. Group comparisons of SSP and SCL-35 scores were carried out with univariate ANOVA, using the general linear models module of the SPSS. Besides the group factor, the ANOVA model included the potential confounders gender and age, which were entered one at a time and kept in the model if at least approaching statistical significance (P B/0.10). Post-hoc pair-wise comparisons of each annoyance group versus the reference group were made with the least significant difference (LSD) procedure on estimated marginal means from the final model. Corresponding group comparisons of LSHC and work load and recovery ratings were carried out with Fisher’s exact test (one-sided) on dichotomized scores. LSHC scores were dichotomized as presence/absence of complaints once weekly, or more often, for any item within each of the eight subscales. The dichotomization of the work load and recovery items was guided by initial analyses of the distribution of ratings on each item in the reference group, showing that, for most items, the more negatively valued ratings were uncommon (typically given by 5 15% of the referents), why ratings were dichotomized at those break points. P -values B/0.05 were considered statistically significant. Effects sizes are expressed as partial eta squares (h2p).

SSP Dimension and Scale

The reply categories to separate items are presented below in conjunction with the results.

Table 1 Swedish universities Scales of Personality (SSP) mean raw scores in the groups of electrically annoyed (EA), smell-annoyed (SA), generally annoyed (GA), and reference subjects

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Age and gender were included in the ANOVA model where appropriate, and P -values have been adjusted accordingly; h2p, partial eta squared; GSI, global severity index.

B/0.001 B/0.001 B/0.001 B/0.001 0.041 0.105 0.054 0.032 0.20 0.13 0.25 0.22 0.75 0.62 0.70 0.73

0.27 0.98 0.17 1.46 0.40 1.15 0.35 1.11

0.42 0.31 0.30 0.29

0.13 0.75 0.08 0.69 0.10 0.55 0.21 0.69

0.83 0.69 0.50 0.63

0.33 1.50 0.15 1.23 0.30 1.30 0.31 1.29

0.25 0.15 0.10 0.20

0.08 0.58 0.06 0.46 0.10 0.30 0.09 0.46

B/0.001 B/0.001 B/0.001 B/0.001

0.001 0.001 B/0.001 B/0.001

GA versus Ref. P SA versus. Ref. P Q1 Q 3

Median

Q1 Q3

Median

Q1 Q3

Median

Q1 Q3

h2p

EA versus Ref. P

Post-hoc t-test ANOVA group Referents (n/54) GA (n/39)

P

Somatization Depression Anxiety GSI

Employment The pattern of formal employment characteristics were similar across groups, for example, concerning type and duration of present employment, working hours, and overtime per week. Satisfaction with

Median

Work load and recovery Only data given by subjects with employment as their main source of income were analysed (EA: n / 15; SA: n/25; GA; n /34; referents: n /50).

SA (n/29)

Lund Subjective Health Complaints (LSHC) Compared to referents, reporting health complaints to occur at least once weekly was more common in the GA group across all eight scales (P 5/0.018; Table 3), and in the EA group on the five scales asthenia/depression, pain, loss of appetite, constipation/heat flushes, and ‘other complaints’ (P 5/ 0.025). In contrast, in the SA group, health complaints occurring at least once weekly were significantly more common than among referents only for the scale Constipation/heat flushes (P /0.019), albeit bordering on statistical significance on the scale ‘other complaints’ (P /0.055). Moreover, the rate of daily complaints were generally higher in the environmental annoyance groups: while only 11% of the referents reported one or more health complaint to occur daily (across all 29 items), this was reported by no less than 69% of the EA subjects, 54% of the GA subjects, and 24% of the SA subjects (P B/0.001, B/0.001 and /0.109, respectively; Fischer’s exact test).

EA (n/16)

Symptom Checklist-35 (SCL-35) ANOVA group differences were found across all scales; somatization (P B/0.001; h2p /0.20), depression (P B/0.001; h2p /0.13), anxiety (P B/0.001; h2p / 0.25), and the total summary score GSI (P B/0.001; h2p /0.22). Post-hoc analyses showed that the EA and GA groups had similar strong elevations across all three SCL-35 subscales and on the GSI, compared to referents (post hoc P /0.001; Table 2). The SA group showed slighter and partial elevations; reaching statistical significance on the somatization (posthoc P /0.041) and GSI (post-hoc P 5/0.032) scales, and bordering on statistical significance on the anxiety scale (0.30 versus 0.10; post-hoc P /0.054), but not showing any clear elevation on the depression scale (post-hoc P /0.105).

SCL Scale

slightly higher mean score than referents on the Psychic Trait Anxiety scale, bordering on statistical significance (post-hoc P /0.052). None of the scales within the dimensions aggressiveness and extraversion showed any group difference.

Table 2 Symptom Checklist 35 (SCL-35) median raw scores in the groups of electrically annoyed (EA), smell-annoyed (SA), generally annoyed (GA), and reference subjects

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236 Table 3 Percentages of subjects in the groups of electrically annoyed (EA), smell-annoyed (SA), generally annoyed (GA), and reference subjects reporting health complaints at least once a week on any item within each subscale of the Lund Subjective Health Complaints (LSHC) LSHC subscale

EA (n/16) (%)

SA (n/29) (%)

GA (n/39) (%)

Referents (n/54) (%)

Fischer’s Exact Test (one-sided) EA versus Ref. SA versus Ref. GA versus Ref. P P P

Asthenia/depression Pain Gastrointestinal Heart/respiratory Loss of appetite Headache Constipation/heat flushes Other complaints

100 69 50 31 25 44 50

62 52 31 24 10 21 24

85 72 56 33 38 54 38

44 37 26 13 2 22 6

B/0.001 0.025 0.067 0.096 0.008 0.086 B/0.001

0.096 0.145 0.402 0.161 0.120 0.553 0.019

B/0.001 0.001 0.003 0.018 B/0.001 0.002 B/0.001

81

69

79

48

0.018

0.055

0.002

present working hours was also similar across groups (data not shown). However, security of employment was rated as ‘more or less insecure’ or lower (‘moderately insecure’ or ‘highly insecure’) by more EA subjects compared to the referents (47 versus 14%; P /0.012), and a tendency in the same direction was seen among GA subjects (31%; P /0.056).

Work situation General displeasure at work was equally common in all groups, with around 40% reporting displeasure at work occurring ‘a few days per month’ or more often. However, rating the satisfaction with present work situation as a whole as ‘neither good nor bad’ or lower (ie, ‘rather bad’ or ‘very bad’), was more common among environmentally annoyed subjects; 36% of the EA, 36% of the SA, and 39% of the GA subjects, compared to only 6% among referents (P 5/0.002). Satisfaction with task assignment was also generally less common among environmentally annoyed subjects, with ratings ‘neither good nor bad’ or lower among 20% of the EA, 28% of the SA, and 36% of the GA subjects compared to 4% of the referents (P 5/0.006 for SA and GA subjects, P / 0.079 for EA subjects). Whereas fairly equal proportions of the groups were satisfied with their quantitative achievements at work (72 87% rated being satisfied ‘rather often’ or ‘very often/always’), a tendency was seen towards more EA subjects (33%) rating their satisfaction with the quality of their work performance to occur only ‘occasionally’ or less often (ie, ‘seldom’ or ‘almost never’), compared to referents (12%; P /0.067). Moreover, a higher proportion of SA subjects rated satisfaction with their personal problem-solving ability at work to occur only ‘occasionally’ or less often, compared to the referents (24 versus 6%; P /0.035).

Social interactions at work A tendency towards more EA subjects than referents reporting a ‘neither good nor bad’ or lower satisfaction with their own ability to maintain good relationships with their colleagues (29 versus 10%; P / 0.096) was observed, but no statistically significant group differences were found concerning general satisfaction with colleagues (data not shown). Awareness of harassment or bullying of fellow workers during the past 6 months was only reported by a higher proportion of GA subjects compared to referents (26 versus 10%; P /0.047). However, eyewitness observations of harassment/bullying episodes were less common and not statistically significantly different across groups. Being a victim of harassment/bullying at the workplace during the last 6 months was more commonly reported only by GA subjects, compared to referents (15 versus 2%; P /0.038). Fatigue and recovery Mental fatigue after work was more commonly reported to occur often among environmentally annoyed subjects; ‘most days’ or ‘every day’ among 47% of the EA, 32% of the SA, and 50% of the GA subjects, but only among 12% of the referents (P 5/0.040). To become thoroughly rested after a workweek, 40% of the EA and SA subjects and 58% of the GA subjects reported needing 2 3 days or longer off work, while only 16% of the referents reported this need (P/0.061, 0.027, and B/0.001, respectively). No statistically significant group difference was seen regarding preferred minimum sleep duration per night (mean 7.5 hours), however the total amount of sleep was reported as ‘slightly insufficient’ or worse (‘moderately’ or ‘highly’) by 60% of the EA, 56% of the SA and 47% of the GA subjects, but only by 30% of the referents (P /0.037, 0.027, and 0.087, respectively). Only the EA group had a clearly higher proportion of subjects (40%)


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reporting ‘rather poor’ or ‘very poor’ quality of sleep in general compared to referents (12%; P /0.024). Only the GA group had a clearly higher proportion of subjects (50%) reporting being in need of a good nights sleep (sleeping through) ‘most days’ or ‘always’, compared to referents (12%; P B/0.001), although a tendency in the same direction was also seen in the SA group (28%; P /0.083). More EA subjects than referents reported an insufficient amount of sleep during workdays, with 64% reporting ‘clearly’ or ‘severely’ insufficient sleep compared to 16% among referents (P /0.020). A similar pattern was found for weekends/holidays, with 33% of the EA subjects reporting ‘clearly’ or ‘severely’ insufficient sleep compared to 2% among referents (P /0.002).

Discussion This study showed that persons with annoyance attributed to electromagnetic fields (the EA group), and to a combination of smells and electromagnetic fields (the GA group), had generally higher levels of trait neuroticism, and reported higher levels of current mental distress and a wider range of subjective health complaints occurring frequently, compared to demographically similar referents. Persons with annoyance attributed to smells only (the SA group) showed a more circumscribed deviation pattern compared to referents, comprising a tendency of elevation on only the psychic trait anxiety subscale within the trait neuroticism dimension, slightly elevated mental distress, and only partially, a higher rate of subjective health complaints. A general finding in the environmentally annoyed groups examined in this study was the higher rates of dissatisfaction with their work situation, including more frequent fatigue after work and a higher, and often unfulfilled, need for recovery. Our results correspond well with the findings of previous studies of clinical patients with IEI. Elevations on certain scales within the trait anxiety dimension of the Karolinska Scales of Personality (a dimension equivalent to the neuroticism dimension of the SSP), have been shown among patients with perceived electrical hypersensitivity,32 and, to a limited extent, among cases of MCS.17,33 A number of studies have also documented the commonness of psychiatric disorders in cases of IEI, particularly somatoform, mood, and anxiety disorders.34,35 However, to our knowledge, the present study is the first to examine the personality of occupationally active non-patients attributing annoyance to smells or electrical equipment in their everyday life. As previously reported,23 only a minority of the sub-

jects in the present groups reported a severity of environmental annoyance reactions that fulfilled the established criteria for ‘self-reported MCS’ or electrical sensitivity’ in the extensive Questionnaire on Chemical and General Environmental Sensitivity (CGES).26 Thus, the finding of elevated neuroticism/ trait anxiety also in this non-patient population sample suggests that the reported high prevalence of emotional problems among clinical IEI patients might not reflect only secondary reactions to living with a disabling hypersensitivity, which is poorly understood by the health care system. It rather suggests that emotional vulnerability as a dispositional characteristic might play a major role in the acquisition and development of environmental intolerance reactions. However, even among the present sample of environmentally annoyed, but otherwise healthy subjects, it cannot be ruled out that their subjective hypersensitivity to smells and electrical equipment had, to some extent, affected daily living and, if so, may have led to altered behaviors and attitudes, influencing the responses to some questions in the personality inventory. The participants were, in the standard way, instructed to reply to all SSP items in terms of ‘how you usually feel or act, not how you feel at present’, and most of the SSP items concern attitudes and behaviors that have been shown to be stable in adulthood.27 For example, concerning psychic trait anxiety, the questions mainly deal with self-confidence, insecurity and sensitivity in social contexts, and in the Somatic Trait Anxiety scale, the questions refer to habitual muscular tension, restlessness, over-reaction to sound, and so on. However, two of the seven questions within the Stress Susceptibility scale concern the ability to concentrate and fatigability, which might hypothetically lead to more confirmatory responses if, for example, involuntary exposure to chemical scents or electrical equipment regularly provokes fear or state anxiety. Although this warrants some degree of caution when interpreting the scores on the Stress Susceptibility scale, it seems unlikely that secondary reactions due to attributions to environmental factors would explain the elevations on most other scales within the trait anxiety/ neuroticism dimension, where the questions are focused on social attitudes and behaviours. A more definite answer to the issue of the causal role of trait anxiety for the development of attribution of annoyance to environmental factors would, however, require a longitudinal study of a very large population sample, probably across decades. However, even among healthy women without self-reported environmental annoyance, the degree of trait psychasthenia (measured with the KSP and equivalent


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to the SSP Stress Susceptibility scale) has been shown to be related to the rate of increasing annoyance during chemical odor provocation.36 This suggests that some aspects of trait anxiety might have a fundamental role for environmental annoyance reactions. It has, on the other hand, also been shown that a large percentage of individuals with no known history of emotional problems are at risk of developing IEI-like conditions in the aftermath of extraordinarily stressful life events. For example, a substantial number of the military personnel deployed in the Persian Gulf War developed sensitivity to chemical smells.37 This brings into focus the everyday life conditions reported by the environmentally annoyed persons under study. Although the pattern of formal employment characteristics, such as duration of present employment and working hours per week, were similar among referents and environmentally annoyed persons, dissatisfaction with various aspects of the work situation was more commonly reported by the latter group. Mental fatigue after work and lack of recuperation was also substantially more commonly reported by the environmentally annoyed persons. These observations were corroborated by similar findings in a parallel 14-day monitoring study of everyday stress and health complaints, which did not seem to be explained only by anticipated or ongoing environmental annoyance (Persson, unpublished observations). Initially, these data seem to indicate that the environmentally annoyed persons had higher mental strain in their everyday life, but this cannot be verified because our design did not include any ‘objective’ measurement of stress at the workplace, eg, an observational study of workplace conditions. However, in a parallel study of the present groups of environmentally annoyed persons, we did not find evidence of an elevated or otherwise disrupted diurnal rhythm of cortisol secretion, nor did we find any abnormality in the functioning of the hypothalamic pituitary adrenal axis, as measured by a dexamethasone suppression test.24 Thus, it remains an open question whether the higher levels of everyday stress, and lack of recovery reported by the environmentally annoyed groups, should be regarded solely as the everyday manifestation of higher trait neuroticism, or might also reflect a higher mental load in everyday life, possibly contributing to the development of environmental annoyance through elevated arousal or state anxiety. It is, however, reasonable to assume that elevated trait neuroticism is related to a generally more negative perception of life events, and necessitates a higher level of effort in order to cope effectively

with the normal demands of life, explaining the higher perceived (reported) level of stress and need for recovery, and the less satisfying social relations found in the environmentally annoyed groups. In recent years, the specific role of anxiety in the acquisition of IEI has been increasingly studied. Elevated arousal and trait anxiety (also called neuroticism or negative affectivity)38 have been experimentally shown to boost the susceptibility to classical conditioning of annoyance to negatively valenced odors (foul smells) and fear-relevant imagery.39 42 A spontaneous spread to other similar odors (ie, stimulus generalization) has also been experimentally verified, again with a particularly strong effect found among persons with high negative affectivity.43 Moreover, alarming information about chemical pollution and MCS (ie, inducing fear of chemicals) has been experimentally shown to lead to symptom learning, also with positively valenced odors, such as eucalyptus oil,44 which might explain the generalization of attribution to perfumes and other ‘pleasant’ smells reported by many persons with MCS. Thus, current data indicate that anxiety might be an important baseline factor for the acquisition of MCS through processes of classical conditioning, operant conditioning, and modeling (Figure 1).45 In this perspective, the process may evolve from a particular sensory cue that happened to be present when annoyance initially emerged, for example, the visual perception of a computer screen or the olfactory perception of fresh paint (classical conditioning). Following spontaneous generalization, the sense of relief associated with withdrawal from trigger situations, may lead to a negative reinforcement of the avoidance behavior (operant conditioning), while impeding the natural extinction process that would otherwise be the result of repeated exposures to triggers. Avoidance might also sharpen the attentive focus on potential triggers and bodily sensations, in order to further predict and avoid trigger situations. Cognitive factors, for example a fear of man-made ‘synthetic’ components of the environment, such as electromagnetic fields and chemical products, induced by alarming reports in mass media or conveyed through popular beliefs, may also act to reinforce, perpetuate, and rationalize withdrawal from offending agents.46 If the individual seeks medical advice for what he/she perceives as an ‘allergy-like’ condition, the clinician specialty encountered might also shape the attribution and sustain the patient’s belief of suffering from a serious disease (modeling).47,48 Thus, various diagnostic labels, such as ‘MCS’, ‘electrical allergy’, ‘chronic fatigue syndrome’, etc., may evolve, depending on the conditioning context,


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Figure 1 An illustration of the basic components and learning processes involved in a model for the development of environmental intolerance reactions, based on the description by Guglielmi et al .45 MCS/IEI, multiple chemical sensitivity/idiopathic environmental intolerance.

the medical specialty of the diagnostician, and the illness belief system of the patient.3,49 In essence, the findings by us and others seem to support the notion that anxiety-related personality traits might contribute to the development and perpetuation of attribution of health complaints to common environmental factors that are tolerated by most people.50 If so, cognitive-behavioral therapy might prove effective, as shown for related conditions, such as fibromyalgia,51 and chronic fatigue syndrome.52,53 A suitable behavioral treatment package would possibly address the classical conditioning by systematic desensitization, the operant conditioning by everyday in vivo exposure, and the maladaptive cognitions by education in basic toxicology and cognitive restructuring. As yet, the

effectiveness of this behavioral treatment package has preliminary support through a few minor treatment studies of MCS cases.45,54,55 A large-scale treatment study seems to be urgently required, both to assess the validity of the learning model for IEI, and, foremost, in order to establish an effective treatment that can be offered to suffering individuals.

Acknowledgements The study was supported by The Swedish Council for Working Life and Social Research, Grant No. 2001-0321 and 2001-0322. Thanks are due to Birgitta Malmberg, MD, for medical examinations and to Lisbeth Prahl for administrative work.

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