SUBTYPING HOARDING DISORDER PATIENTS BASED ON THEORY of MIND - A COMPARATIVE STUDY WITH OCD and PDD PATIENTS

Abstract Introduction Theory of Mind (ToM) is the ability to represent one's own or another person's mental state, and is impaired in various psychiatric illnesses, but most strikingly in patients with Autism Spectrum Disorder (ASD) [1] . Within the scope of a transdiagnostic approach across disorders characterized by repetitive and ritualistic behaviour, the aim of the present study was to 1) compare patients with ASD, Hoarding Disorder (HD) and Obsessive-Compulsive Disorder (OCD), on ToM functioning, and 2) to study patient profiles across study groups based on ToM performance. Method The study was approved by the ethical review board of the UMC Utrecht. A total of 89 participants were recruited: 17 ASD-, 27 OCD-, 22 HD-patients and 23 controls. Clinical characteristics were assessed with respect to hoarding, obsessive-compulsive, autism, ADHD and inhibition/ approach symptoms. ToM functioning was assessed with the aid of the Faux pas test [2] . This story test measures: total ToM capacity, detection of Faux pas in the story, the skills to determine the content of a social situation, false belief (a misconception resulting from incorrect reasoning) and empathy. Results No between-group differences were found between ASD,HD,OCD and controls when groups were compared on the Faux pas total or subscales. When study subjects were regrouped based on performance on the Faux pas (into a low, average and high performance group), results revealed that subjects with low performance on the Faux pas showed lower behavioral approach scores, higher ADHD total and inattention scores, and higher Autism communication and hoarding scores. Further, when grouped based on performance on the false belief subscale, as expected most (71%)of the ASD subjects were in the ‘low’ or ‘average’ performance domain, whereas most of the OCD patients (88%) and controls (95.6%) were in the ‘average’ or ‘good’ domain. Strikingly, HD patients showed a bimodal pattern; with 36.4% scoring in the "low" performance and 41% scoring in the "high" performance domain. HD patients with low false belief performance reported low behavioral approach scores, low OC symptom scores and high ADHD total and inattention scores, while HD patients with good false belief performance showed high OC symptom scores and low ADHD scores. Conclusion These data indicate that ASD, HD and OCD show striking similarities with respect to symptom profiles and ToM when studying classical between-DSMIV group comparisons. Howeve