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, η_p² =.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).