Distinct clinical manifestations of obsessive-compulsive disorder are associated with cortical thickness alteration.

Background: Although brain structural changes have been reported in patients with obsessive-compulsive disorder (OCD), results from previous studies have been inconsistent. A growing number of studies have focused on obsessive beliefs and impulsivity which could be involved in the occurrence and maintenance of OCD symptoms. The present study aimed to examine whether there are distinct brain structural changes in patients with different OCD subgroups.

Methods: Eighty-nine patients with OCD and 42 healthy controls were recruited to undergo structural magnetic resonance imaging brain scan. OCD patients were classified into subgroups according to scores of the Obsessive Belief Questionnaire (OBQ-44) and the Barratt Impulsiveness Scale (BIS-11) using cluster analysis. Group comparisons in cortical thickness and subcortical volumes between all OCD patients and healthy controls, as well as between subgroups of OCD patients and healthy controls, were carried out.

Results: OCD patients with more obsessive beliefs and attentional impulsivity (OCD_OB_AT) had reduced cortical thickness at the inferior parietal gyrus, the superior and middle temporal gyrus and the insula compared with OCD patients with higher score on the non-planning impulsivity (OCD_NP, corrected  < 0.05). The whole group of OCD patients and both subgroups showed reduced cortical thickness at the superior parietal gyrus compared with controls (uncorrected  < 0.01, number of vertices > 100).

Conclusion: Our results suggest that apart from distinct phenomenology, there are distinct neural correlates of different OCD subgroups based on obsessive beliefs and impulsivity. These neural correlates may have clinical significance and should be considered in future research.