White matter alterations associate with onset symptom dimension in obsessive-compulsive disorder

The high heterogeneity of obsessive-compulsive disorder (OCD) is best described by a multidimensional model involving symptom dimensions. We aimed to investigate white matter alterations associated with OCD, focusing on the impact of long-lasting effect of symptom dimensions assessed at onset of illness. Furthermore, we investigated white matter alterations associated with this disorder, controlling for the impact of medications and for the prevailing current symptom dimension.

We studied 58 patients affected by OCD and 58 age- and sex-matched healthy controls. We divided patients according to symptom dimension at onset of illness, assessed with the five-factor model. T-tests were performed in order to investigate differences between subgroups. Similar analyses were performed considering the prevailing current symptom dimension. Analyses were conducted with tract-based spatial statistics on diffusion tensor imaging.

Doubt/checking and rituals/superstition symptom dimensions at onset and symmetry/perfectionism current symptom dimensions were characterized by significant alterations in diffusion tensor imaging measures. An association of white matter alterations and symmetry/perfectionism current dimension was found only when controlling for the effect of doubt/checking dimension at onset. Finally, results pointed out that the observed differences between patients and healthy controls were carried by the effect of previous and current medications.

Our findings evidenced that onset symptom dimensions are associated with enduring alterations of white matter microstructure. Onset symptom dimensions may reflect underlying endophenotypes. In addition, present results confirm the effect of medications on white matter in OCD, showing a large effect of current treatment on myelination.