Original ArticlesDifferential Resting Quantitative Electroencephalographic Alpha Patterns in Women with Environmental Chemical Intolerance, Depressives, and Normals
Introduction
Self-reported illness from the odors of low, presumably “nontoxic” levels of environmental chemicals (CI, chemical intolerance), including difficulty concentrating, dysphoric mood, and multiple somatic symptoms, is emerging as a significant public health problem, especially in women (Ashford and Miller in press). Prevalence studies in nonindustrial samples have demonstrated a rate of 15–30% for mild to moderate, and of 4% for severe CI (Bell et al 1993a, Bell et al 1993b, Bell et al 1993d, Bell et al 1994, Bell et al 1996a, Bell et al 1996dBell et al in press a, Bell et al in press b; Meggs et al 1996; Wallace et al 1991). Workers with occupational solvent exposure report CI at the high rate of 60% (Morrow et al 1990). The clinically severe cases, generally labeled multiple chemical sensitivity (MCS, Cullen 1987), usually a) involve numerous lifestyle changes to avoid chemicals (Bell et al 1995a; Simon et al 1990); b) overlap symptomatically with other controversial conditions such as chronic fatigue syndrome (CFS) and fibromyalgia (Buchwald and Garrity 1994; Fiedler et al 1996); and c) lead to increased rates of disability (Bell et al 1995a; Black et al 1990; Miller and Mitzel 1995; Simon et al 1990). Unlike CFS, MCS per se does not yet have a generally accepted case definition (Cullen 1987; Miller 1994). Societal implications of the problem include increased worker absenteeism, disability claims, litigation (Simon et al 1990), and high utilization of health care services (Buchwald and Garrity 1994).
Although the interpretation remains in dispute (Davidoff and Fogarty 1994; Terr 1993), and a substantial subset of MCS patients do not have any psychiatric diagnoses (Fiedler et al 1996; Simon et al 1993), the available data nonetheless indicate increased depression ratings in many persons with CI (Bell et al 1993a, Bell et al 1993b, Bell et al 1993c, Bell et al 1994, Bell et al 1996a, Bell et al in submission a, Bell et al in submission b, Bell et al in submission c) and MCS (Bell et al 1995a; Simon et al 1990, Simon et al 1993). These findings include elevated depression subscale scores on the Symptom Checklist 90 (revised) and the Beck Depression Inventory (Bell et al 1996b; Doty et al 1988), as well as significantly increased lifetime prevalence of major depression diagnoses, e.g., from 30% (Black et al 1990) to 54% (Bell et al 1995a; Simon et al 1990), in CI and MCS compared with lower rates in various control groups. Recently, Fiedler et al (1996)reported that CI who cannot identify a clear date of onset for their condition associated with a specific chemical exposure and CFS have high rates of psychiatric disorders, notably depression (e.g., 54% in CI and 67% in CFS versus only 30% in MCS with a self-identified chemical initiation event and 11% in normals).
Electroencephalography (EEG) may offer an objective tool to delineate the pathophysiology and subtypes of chemical intolerance (Bell 1994, Bell 1996; Bell et al 1992; Benignus 1984; Muttray et al 1995; Schwartz et al 1994; cf., Prichep and John 1992) and to compare affectively disturbed CI and MCS with depressives. Staudenmayer and Selner (1990), for example, compared resting qEEG patterns at the right parietal site P4 of MCS clinic patients with those of a mixed group of psychologically disordered outpatients with unspecified levels of CI, and controls without psychopathology but with various medical conditions. They found similarities in pattern between the MCS and psychologic groups in elevated beta activity (15–25 Hz) and decreased alpha-2 (9.8–12.2 Hz) relative to the medical controls; however, CI by itself does not necessarily lead to the EEG patterns of depression. Nondepressed elderly with CI exhibited decreased rapid-eye-movement (REM) sleep and a trend toward a longer REM onset latency on polysomnographic recording (Bell et al 1996c), a finding contrary to objective sleep EEG parameters usually reported in major depressives (Reynolds et al 1985).
Many (Brenner et al 1986; Pollock and Schneider 1990; Schaffer et al 1983), though not all (Knott and Lapierre 1987; Visser et al 1985) waking quantitative EEG (qEEG) studies suggest that depressives exhibit a) increases in the overall amount of alpha activity; and b) relative right anterior hemisphere activation at rest (asymmetry—less alpha on right than left) (Allen et al 1993; Davidson et al 1979, Davidson et al 1985; Henriques and Davidson 1991; Nystrom et al 1986). Both alpha findings may be trait markers for affective disorder vulnerability; depressives exhibit them even after recovery from the depressed state (Henriques and Davidson 1988; Pollock and Schneider 1989). The frontal alpha finding also predicts individual differences in inhibited (cf., shy) temperament in that infants with resting frontal asymmetry show greater emotional reactivity to the novelty of separation from their mothers (Davidson and Fox 1989). Notably, shyness is a temperamental feature of nondisabled persons with CI (Bell et al 1993a, Bell et al 1993b, Bell et al 1995b, Bell et al 1996a), but not necessarily of disabled MCS patients (Bell et al 1995a). Overall, decreased alpha implies greater mental activation or alertness in attentional function, whereas increased alpha indicates the reverse, e.g., relaxed wakefulness (Niedermeyer and Lopes da Silva 1993; Ray and Cole 1985).
Bell et al (Bell 1994, Bell 1996; Bell et al 1992, Bell et al 1993c, Bell et al 1996bBell et al in submission a, Bell et al in submission b, Bell et al in submission c, Bell et al 1996d, Bell et al in press a, Bell et al in press b) have proposed that the neurobehavioral process of time-dependent sensitization (TDS) (Antelman 1988, Antelman 1994) could explain the progressive and persistent amplification in reactivity to chemicals reported in persons with CI. TDS is the increase in responsivity to a given stimulus (physical or psychological stressors, pharmacologic agents, chemicals) by the passage of time between successive exposures (Antelman 1988, Antelman 1994; Sorg et al 1996; Stewart and Badiani 1993). TDS is a proposed model for the long-term course of craving for addictive substances (Robinson and Berridge 1993; Sills and Vaccarino 1994) as well as of recurrent affective disorders (Post 1992). Animals given repeated intermittent exposures to sensitizing agents can exhibit increases over time in EEG alpha-1 and alpha-2 (Ferger et al 1996—correlated with increased D2 dopamine receptor activation at higher initiating doses) and/or beta responses (Burchfiel and Duffy 1982; Kay 1996). Both functional neuroimaging data (Heuser et al 1994) and visuospatial divided attention and visual memory test abnormalities (Bell et al 1995bBell et al in submission a, Bell et al in submission b, Bell et al in submission c, Bell et al 1995c; Fiedler et al 1996) point to the possibility of right frontal lobe dysfunction in MCS. Notably, dopamine depletion in prefrontal cortex can enhance sensitizability in animals (Deutch et al 1990; Hamamura and Fibiger 1993; Kalivas and Barnes 1993; Mitchell and Gratton 1992). Solvents, which commonly initiate MCS (Miller and Mitzel 1995), can deplete central nervous system dopamine and initiate TDS (Von Euler et al 1994), as well as impair spatial learning in animals (Von Euler et al 1993).
No previous research in human subjects with CI has examined frontal EEG alpha patterns over time in a sensitization protocol. Consequently, the purpose of the present study was to characterize the psychological profiles and resting qEEG absolute alpha patterns, especially in frontal sites, of moderately ill CI with affective distress, depressives without CI, and normals without CI or depression, all recruited from the community rather than from a clinical setting.
Section snippets
Subjects
The subjects were nonsmoking, nonalcoholic (screened by the CAGE questionnaire—Ewing 1984, and by psychiatric/medical interview), nonpregnant women, aged 30–50 years (the gender and age range reportedly most susceptible to MCS—Ashford and Miller in press), in stable medical health. They were recruited by newspaper advertisement and flyers placed in local fitness clubs. The advertisements sought volunteers with and without chemical odor intolerance and with and without depression. Inclusion
Demographics and Psychological Profiles
Table 1summarizes the descriptive features of each group. The CI were significantly older than the other two groups; consequently, all of the qEEG MANCOVA analyses included age as a covariate. The CI also rated their overall health as significantly poorer than did the N. Groups did not differ significantly for educational level, marital status, left-handedness, amount overweight, or Cain olfactory identification ability. Subjects worked in settings involving primarily indoor air environments,
Discussion
The current data suggest that middle-aged, well-educated women with CI and affective distress exhibit a divergent pattern of resting qEEG alpha activity from that of non-CI depressives and normals. That is, the CI group in this study exhibited greater absolute frontal F7–F8 alpha at rest over a 1-week period from session 1 to 2, than did the comparison groups; however, it was only the depressives without CI who showed the asymmetric right frontal activation (less alpha on right than left)
Acknowledgements
This research was supported by a grant from the Environmental Health Foundation.
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