Immunologic, psychological, and neuropsychological factors in multiple chemical sensitivity. A controlled study

Abstract

Objective: To examine the role of immunologic, psychological, and neuropsychological factors in multiple chemical sensitivity.

Design: Case-control comparison.

Setting: Community allergy practice (cases), university-based clinics for musculoskeletal injuries (controls).

Participants: Forty-one patients with chemical sensitivity and 34 control patients with chronic musculoskeletal injuries.

Main outcome measures: Immunologic measures included autoantibody titers, lymphocyte surface markers, and interleukin-1 generation by monocytes. Psychological evaluation included standardized measures of anxiety, depression, and somatization.

Results: Immunologic testing did not differentiate patients with chemical sensitivity from controls. The only difference noted (lower interleukin-1 generation among cases) appeared attributable to laboratory methods. Patients with chemical sensitivity reported greater prevalence of current anxiety or depressive disorder (44% versus 15%, P = 0.006). This difference, however, did not appear to precede the onset of chemical sensitivity, and 25% of chemically sensitive patients showed no significant current psychological disturbance. Cases reported significantly more "medically unexplained" physical symptoms before and after the onset of chemical sensitivity. When considering only symptoms that preceded chemical sensitivity, 25% of cases (and no controls) satisfied criteria for somatization disorder. Neuropsychological testing revealed no significant case-control differences.

Conclusions: Immunologic testing failed to confirm findings from earlier uncontrolled studies, militating against proposed immunologic mechanisms. The decreased memory and concentration frequently described in multiple chemical sensitivity were not confirmed by brief neuropsychological testing. Psychological symptoms, although not necessarily etiologic, are a central component of chemical sensitivity.