Obsessive-compulsive symptom dimensions correlate to specific gray matter volumes in treatment-naïve patients.

Background: Clinical and sociodemographic findings have supported that OCD is heterogeneous and composed of multiple potentially overlapping and stable symptom dimensions. Previous neuroimaging investigations have correlated different patterns of OCD dimension scores and gray matter (GM) volumes. Despite their relevant contribution, some methodological limitations, such as patient's previous medication intake, may have contributed to inconsistent findings.

Method: Voxel-based morphometry was used to investigate correlations between regional GM volumes and symptom dimensions severity scores in a sample of 38 treatment-naïve OCD patients. Several standardized instruments were applied, including an interview exclusively developed for assessing symptom dimensions severity (DY-BOCS).

Results: Scores on the "aggression" dimension were positively correlated with GM volumes in lateral parietal cortex in both hemispheres and negatively correlated with bilateral insula, left putamen and left inferior OFC. Scores on the "sexual/religious" dimension were positively correlated with GM volumes within the right middle lateral OFC and right DLPFC and negatively correlated with bilateral ACC. Scores on the "hoarding" dimension were positively correlated with GM volumes in the left superior lateral OFC and negatively correlated in the right parahippocampal gyrus. No significant correlations between GM volumes and the "contamination" or "symmetry" dimensions were found.

Conclusions: Building upon preexisting findings, our data with treatment-naïve OCD patients have demonstrated distinct GM substrates implicated in both cognitive and emotion processing across different OCS dimensions.