Microbiome in Obsessive-compulsive Disorder

Background: Humans live in symbiosis with microbes and their implication for health and disease is evident. The importance of microbiome-gut-brain axis in psychiatric disorders is an area of increasing research interest. OCD is a promising target for microbiome research as Pediatric Acute-onset Neuropsychiatric Syndrome (PANS)/ Pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections (PANDAS) are reactions to infectious agents precipitating acute onset of severe OCD symptoms. Furthermore, preliminary evidence has associated probiotic treatment with alleviation of OCD symptoms. We propose the first clinical study on the microbiome and its effects on OCD patients. Aim: To analyze the gut microbiota in patients with OCD compared with healthy matched controls and assess changes in microbial composition following treatment. Outcome measures: Differences in alpha diversity, beta diversity, and taxa abundance of bacterial groups (at the phylum, class, order, family, genus and species levels) and severity of OCD symptoms. Moreover, functional profiling will be conducted. Methods: Our aim is to enroll 32 OCD patients and 32 matched controls. Shotgun metagenomic sequencing will be used. Sequenced data will be processed followed by non-parametric statistical testing. Significance: gut microbiome in patients with OCD beofre and after ERP treatment has never been done before. The microbial composition may impact on OCD symptoms, severity, and chronicity and could inform future therapeutic possibilities.