Associations of cortical thickness, surface area and subcortical volumes with insight in drug-naïve adults with obsessive-compulsive disorder

Abstract

Poor insight in obsessive-compulsive disorder (OCD) is associated with several adverse clinical outcomes. However, the neurobiological basis of this insight deficit is not clearly understood. The present study thus aimed to investigate associations of cortical thickness, cortical surface area and subcortical volumes with insight in a sample of drug-naïve adults with OCD. Forty-seven OCD patients and 42 healthy controls (HCs) underwent MRI scanning, depression and anxiety assessments. The Brown Assessment of Beliefs Scale (BABS) measured insight levels and patients were divided into two groups: poor insight (OCD-PI; n = 21), and good insight (OCD-GI; n = 26). Cortical thickness and surface area between groups were compared with whole-brain exploratory vertex-by-vertex analyses, while subcortical volumes were compared on a structure-by-structure basis. Partial correlation analyses were then performed to assess associations between regional cortical and subcortical measures and insight levels. OCD-GI and OCD-PI groups displayed partly shared, but also partly distinct brain structural alterations. Strikingly, OCD-PI showed decreased cortical thickness in the left superior frontal gyrus, left anterior cingulate cortex (ACC) and right inferior parietal gyrus, compared to both OCD-GI and HCs. Average cortical thickness extracted from these areas was further negatively correlated with BABS scores in the OCD-PI patients. Our findings suggest that poor insight in patients with OCD may have a neural substrate involving the left medial frontal and the right inferior parietal cortices.

Keywords: Cortical thickness; Insight; Obsessive-compulsive disorder; Surface-based morphometry.

Fig. 1

(A) Brain regions exhibiting differences in cortical thickness between OCD-GI and HC. (B) Brain regions exhibiting differences in cortical thickness between OCD-PI and HC. (C) Brain regions exhibiting differences in cortical thickness between OCD-PI and OCD-GI. Results are shown at p < 0.05 corrected for multiple comparisons with Monte-Carlo simulation. Clusters color-coded in blue indicate significantly decreased cortical thickness in the OCD-PI group compared to either the OCD-GI or HCs or in the OCD-GI group compared to the HCs. Clusters are overlaid on average inflated images with sulci displayed as dark relative to gyri.

Fig. 2

Scatter plots showing significant negative correlations between BABS scores and average cortical thickness in the superior frontal cluster in OCD-GI group (A) and OCD-PI group (B); and in the right inferior parietal cluster in the OCD-GI group (C) and OCD-PI group (D), controlling for the Y-BOCS score (significant with Bonferroni-Holmes correction [0.05/2]).