Somatization is associated with deficits in affective Theory of Mind

Objective: To determine whether deficits in mental representation of emotion may constitute a mechanism for somatization.

Methods: In this case-control study, we obtained measures of cognitive and affective Theory of Mind, emotional awareness, positive and negative affect, depression, anxiety, and physical symptoms and determined psychiatric diagnoses in consecutive outpatients, aged 19 to 60, with Conversion Disorder (n=29), Functional Somatic Syndromes (n=30), or "explained" Medical Disorders (Controls) (n=30). Main outcome measure was the Animations-L score, i.e., use of words describing emotional content while performing the Frith-Happé Animations (video) Task, an established Theory of Mind measure in which the emotional content of a story is conveyed through movement.

Results: Groups were similar in number of physical symptoms, negative affect, and ability to describe emotional experiences on a written measure that specifically solicited such descriptions. Conversion Disorder and Functional Somatic Syndrome groups scored lower on Animations-L, endorsed significantly less positive affect, and had more anxiety than Medical Controls. Animations-L and positive affect scores were predictive of group membership, with lower scores predicting somatizing conditions.

Conclusions: Relative to Medical Controls, a deficit in the encoding and reporting of emotion when the emotional content of the stimulus is conveyed in action occurs equally in Conversion Disorder and Functional Somatic Syndrome patients and is consistent with previous findings in somatoform disorder inpatients. Difficulty with "conversion" from implicit (action, somatic) to explicit (representational) processing of emotions, exacerbated by anxiety, may constitute a mechanism for somatization.