Conversion disorder and multiple chemical sensitivity: a comparative study of psychological defense strategies

Exploratory Investigation of a Brief Cognitive Behavioral Intervention and Transcranial Direct Current Stimulation on Odor Sensitivity

OBJECTIVE

Enhanced odor sensitivity is a phenomenon that potentially underlies conditions such as multiple chemical sensitivity (MCS). Currently, there are no treatments that have been shown to effectively decrease odor sensitivity. Given similarities of odor hypersensitivity/MCS to pain sensitization disorders such as fibromyalgia, there may be a potential for interventions that improve pain tolerance to modulate odor sensitivity.

METHODS

This exploratory study randomized 72 healthy community adult volunteers to receive one of six treatments in between two assessments of thermal pain tolerance and odor threshold. Participants were randomized to receive either cathodal, anodal, or sham transcranial direct current stimulation (tDCS) aimed at dorsolateral prefrontal cortex. In addition, participants were provided a brief cognitive behavioral intervention (CBI) for pain consisting of task framing, cognitive restructuring, and distraction technique training, or a control intervention consisting of information about pain.

RESULTS

Persons who received a brief CBI showed significantly increased odor thresholds (reduced sensitivity) during intervention (F (1,62) = 7.29, p = .009, ηp = .11), whereas the control intervention was not associated with altered odor thresholds. Moreover, in those who received brief CBI, more severe anxiety associated with larger reductions in odor sensitivity (ρ = .364, p = .035). There was no effect of tDCS (F (2,62) = .11, p = .90) nor interaction between tDCS and CBI (F (2,62) = .32, p = .73).

CONCLUSIONS

Given the connection between anxiety and MCS, results suggest that CBT techniques for somatic processes may show promise in treating conditions characterized by increased sensitivity to odors (e.g., MCS).

Possible influence of defenses and negative life events on patients with chronic fatigue syndrome: a pilot study

13 patients with a diagnosis of chronic fatigue syndrome and two contrast groups of conversion disorder patients (n = 19) and healthy controls (n = 13) were assessed using the projective perceptual Defense Mechanism Test to investigate if specific defense patterns are associated with chronic fatigue syndrome. Another objective was to assess the possible influence of perceived negative life events prior the onset of the illness. The overall results showed significant differences in defensive strategies among groups represented by two significant dimensions in a Partial Least Squares analysis. Compared to the contrast groups the patients with chronic fatigue syndrome were distinguished by a defense pattern of different distortions of aggressive affect, induced by an interpersonal anxiety-provoking stimulus picture with short exposures. Their responses suggested the conversion group was characterized by a nonemotionally adapted pattern and specific constellations of defenses, associated with interior reality orientation compared to the patients with chronic fatigue syndrome and the healthy controls. Rated retrospectively, the group with chronic fatigue syndrome reported significantly more negative life events prior to the onset of their illness than healthy controls. For instance, 5 of the 13 patients reported sexual assault or physical battery as children or teenagers compared to none of the healthy controls. A significant association was found between defense pattern and frequency of reported negative life events. However, these retrospective reports might be confounded to some extent by the experience of the patients' illness; for example, the reports may be interpreted in terms of present negative affect.