Mental rotation of body- and non-body stimuli in body dysmorphic disorder

Individuals with body dysmorphic disorder (BDD) experience a discrepancy between their own and others’ perception of their physical appearance. This discrepancy indicates biased body representations. BDD is associated with distortions in cognitive-affective and perceptual body image, such as high body dissatisfaction or aberrant visual processing. Body representations are also used for movements and actions (e.g., symptom behavior). These aspects of action-oriented body representations have not been examined yet. The aim of the current study was to investigate general mental rotation and mental rotation of body versus non-body targets to capture such action-related representations. Sixty-three individuals (n = 35 BDD participants, and n = 28 mentally healthy controls [HC]) were included and performed two mental rotation tasks of non-body and body-stimuli. The results revealed higher mental rotation accuracy in the HC versus BDD group (t(60.57) = 2.61, p = .011, d = .64) in a paper-pencil task with non-body stimuli (i.e., digits) but no significant group (F(1, 61) = .21, p = .650, ω2 = .000) or group x stimulus effects in a computerized reaction-time task with body- and non-body stimuli. Bayes Analyses were used to assess the strength of evidence for absence of hypothesized specific effects. Although the conclusion should be interpreted cautiously given methodological factors related to task and participant characteristics, the findings suggest that potential distortions in action-related body representations in BDD may not occur on a general body-related level. They may rather be body part-dependent and warrant further investigation, particularly in relation to disorder-relevant body regions.