Severity related neuroanatomical alteration across symptom dimensions in obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a symptomatically heterogeneous disease. Symptoms of OCD can be grouped into a six-factor structure including washing, checking, neutralizing, obsessing, ordering and hoarding. These different symptom profiles might be one of the critical factors contributing to the inconsistent neuroanatomical findings in OCD according to the literature. In this study, whole-brain voxel-based morphometry was used to examine neuroanatomical alterations in gray matter (GM) for OCD compared to healthy controls, and the variations associated with differing symptoms of OCD. The high-quality structural imaging data from 39 OCD individuals and 42 age-matched healthy controls were recruited. First, we found increased cortical GM volume in the left postcentral gyrus in OCD participants compared to healthy controls. Next, six independent regression analyses were conducted to examine the correlation between OCD symptom dimensions and inter-individual variation in neuroanatomy. After a rigorous multiple comparison correction, greater hoarding symptom was robustly found associated with greater GM volumes at various frontotemporal regions (including orbitofrontal, middle frontal and superior temporal GMs). Additionally, greater washing symptoms were associated with increased GM volume at the superior temporal cortex. The symptom-specific GM alterations observed here support the notion that OCD is an etiologically heterogeneous disorder, with both overlapping and distinct neuroanatomical structure across symptom dimensions.