Sex differences in neural responses to disgusting visual stimuli: Implications for disgust-related psychiatric disorders

Background: A majority of patients with disgust-related psychiatric disorders such as animal phobias and contamination-related obsessive-compulsive disorder are women. The aim of this functional magnetic resonance imaging (fMRI) study was to examine possible sex differences in neural responses to disgust-inducing stimuli that might help explain this female predominance. Methods: Thirty-four healthy adult volunteers (17 women, all right-handed) were scanned while viewing alternating blocks of disgusting and neutral pictures from the International Affective Picture System. Using a partially-silent fMRl sequence, the participants rated their level of discomfort after each block of pictures. Skin conductance responses (SCR) were measured throughout the experiment. All participants completed the Disgust Scale. Results: Both women and men reported greater subjective discomfort and showed more SCR fluctuations during the disgusting picture blocks than during the neutral picture blocks. Women and men also demonstrated a similar pattern of brain response to disgusting compared with neutral pictures, showing activation in the anterior insula, ventrolateral and clorsolateral prefrontal cortices, and visual regions. Compared with men, women had significantly higher disgust sensitivity scores, experienced more subjective discomfort, and demonstrated greater activity in left ventrolateral prefrontal regions. However, these differences were no longer significant when disgust sensitivity scores were controlled for. Conclusions: In healthy adult volunteers, there are significant sex-related differences in brain responses to disgusting stimuli that are irrevocably linked to greater disgust sensitivity scores in women. The implications for disgust-related psychiatric disorders are discussed.