Increased orbital frontal gray matter volume after cognitive behavioural therapy in paediatric obsessive compulsive disorder.

Abstract Objectives. Identify differences in regional brain volume between medication-free pediatric OCD patients and controls and examine changes after cognitive behavioural therapy. Methods. We assessed 29 medication-free paediatric OCD patients (Age: M = 13.78 years; SD = 2.58; range 8.2-19.0) and 29 controls, matched on age and gender, with T1-weighted MR scans in a repeated measures, pre-post treatment design. Voxel based morphometry (VBM) following diffeomorphic anatomical registration through exponential lie algebra (DARTEL) was used to test voxel-wise for the effects of diagnosis and treatment on regional gray matter (GM) and white matter (WM) volumes. Results. After cognitive behavioural therapy, orbitofrontal GM and capsula externa WM increased in paediatric OCD relative to controls. In patients, changes in symptom severity (delta CY-BOCS) correlated positively with GM volume in the orbitofrontal cortex after treatment. Furthermore, before treatment, paediatric OCD patients, compared to the controls, showed larger GM volume in left frontal pole and left parietal cortex and larger WM volume in cingulum and corpus callosum. Conclusions. Our findings underscore the involvement of the ventral frontal-striatal circuit in paediatric OCD and the plasticity of this circuit in response to the modulatory effects of CBT. The possible relation to brain development is discussed.