Obsessive-compulsive Disorder (OCD) is a heterogeneous psychiatric disorders characterized by obsessive thought and compulsive behaviours. Recent studies also suggest individuals with OCD exhibit dysfunction in the cortico-striato-thalamo-cortical network. However, findings from brain structural changes in OCD are less consistent. Moreover, it is also less clear whether OCD is characterized by altered brain structural asymmetry, a commonly reported marker observed in various psychiatric disorders including schizophrenia spectrum disorders. Biological Psychiatry has just published a study conducted by the OCD Working Group within the ENIGMA (Enhancing Neuro Imaging Genetics through Meta Analysis) Consortium (Kong et al., 2020, Biological Psychiatry, Mapping Cortical and Subcortical Asymmetry in Obsessive-Compulsive Disorder: Findings from the ENIGMA Consortium https://doi.org/10.1016/j.biopsych.2019.04.022). In Kong’s study, they compiled a total of 501 paediatric patients with OCD and 439 healthy controls as well as 1777 adult patients with OCD and 1654 healthy controls, and specifically examined cerebral asymmetry phenomenon in OCD patients. Their findings confirmed altered asymmetry of subcortical structures in paediatric OCD patients. However, such subtle changes were not easily detected in adult OCD patients.

Dr. Raymond Chan from Neuropsychology and Applied Cognitive Neuroscience (NACN) Laboratory, CAS Key Laboratory of Mental Health, Institute of Psychology was invited to make a commentary on these findings. Dr. Chan’s team highlighted the altered cerebral asymmetry found in paediatric but not adult OCD patients may suggest the important role of the thalamus and the pallidum during early neuropathological development of OCD. These two brain regions play an important role in the cortico-striato-thalamo-cortical network underlying the observed clinical and behavioural manifestations in OCD patients. Moreover, Dr. Chan’s team also commented that the effect of asymmetry in OCD patients was most noticeable on left hemispheric dominance, an altered cerebral asymmetry which is also commonly found in schizophrenia patients. It is clinically and theoretically interesting to see both schizophrenia patients and OCD patients share commonalities in altered subcortical volume and asymmetry. The cortico-striato-thalamo-cortical is believed to be the underlying network responsible for compulsivity, whilst the frontal-striatal-thalamic circuits have been found to be dysfunctional in patients with psychosis, and familial and behavioural high-risk populations prone to develop psychosis.

Dr. Chan’s previous neuroimaging study also showed that patients with schizo-obsessive commorbidy suffered altered functional connectivity of the default mode network, decreased grey matter volume of the left thalamus, decreased cortical thickness of the right supplementary motor area, the occipital and temporal gyri. These findings provide neurobiological evidence to support the obsessive-compulsive dimension in schizophrenia. Taken together, a transdiagnostic approach recruiting large-scale samples is useful for us to examine whether cerebral and cerebellar asymmetry is promising biomarker to delineate early neuropathological changes before the onset of the disorders. Dr. Chan has recently established a Transdiagnostic Clinical and Subclinical Research Centre to promote research for transdiagnostic clinical and subclinical samples.

This work was supported by the National Key Research and Development Programme, and the CAS Key Laboratory of Mental Health, Institute of Psychology.

This commentary is now published online in Biological Psychiatry 
Wang, Y., Wang, Y. M., Lui, S. S. Y., Chan, R. C. K.* (2020). Clinical implication of brain asymmetries in psychiatric disorders. Biological Psychiatry, 87, 1014-1016.

Related papers
Kong XZ, Boedhoe PSW, Abe Y, Alonso P, Ameis SH, Arnold PD, et al. (2020):Mapping Cortical and Subcortical Asymmetry in Obsessive-Compulsive Disorder: Findings From the ENIGMA Consortium. Biol Psychiatry.

Wang, Y. M., Cai, X. L., Zhang, R. T., Wang, Y., Madsen, K. H., S?rensen, T. A., M?ller, A., Cheung, E. F. C., Chan, R. C. K. * (in press). Searchlight classification based on amplitude of low frequency fluctuation and functional connectivity in individuals with obsessive-compulsive symptoms. Cognitive Neuropsychiatry, https://doi.org/10.1080/13546805.2019.1658575

Wang, Y. M., Zou, L. Q., Xie, W. L., Yang, Z. Y., Zhu, X. Z., Cheung, E. F. C., S?rensen, T. A., M?ller, A., Chan, R. C. K. * (2019). Altered functional connectivity of the default mode network in patients with schizo-obsessive comorbidity: A comparison between schizophrenia and obsessive-compulsive disorder. Schizophrenia Bulletin, 4(1), 199-210. https://doi.org/10.1093/schbul/sbx194

Wang, Y. M., Yang, Z. Y., Cai, X. L., Zhou, H. Y., Zhang, R. T., Yang, H. X., Liang, Y. S., Zhu, X. Z., Mardsen, K. H., S?rensen, T. A., M?ller, A., Wang, Z., Cheung, E. F. C., Chan, R. C. K.* (2020). Identifying schizo-obsessive comorbidity by tract-based spatial statistics and probabilistic tractography. Schizophrenia Bulletin,46(2), 442-453. DOI:10.1093/schbul/sbz073

Wang, Y., Ettinger, U., Meindl, T., & Chan, R. C. K. (2018). Association of schizotypy with striatocortical functional connectivity and its asymmetry in healthy adults. Human Brain Mapping, 39(1), 288–299. https://doi.org/10.1002/hbm.23842