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The root cause of Obsessive-compulsive disorder (OCD) might be more physical than mental, a study by Chinese researchers has found. It states that bacteria living in our gut could be responsible for OCD in most people. The study aimed to understand the link between the gut microbiota and OCD, and whether it plays a role in a person developing OCD. The team identified six types of bacteria that appear to be linked with the condition. Out brain and the gut have often been found to have a connection, with mental health affecting how the digestive system acts. However, this is the first time that scientists have gathered evidence that shows gut bacteria affects mental health conditions.

Researchers from Chongqing Medical University wrote in their published paper, "Previous studies have indicated a potential link between the gut microbiota and OCD. However, the exact causal relationship remains uncertain. Our analysis suggested that specific gut microbiota might have a causal relationship with OCD, revealing potential intervention strategies for the prevention and treatment of this disorder."

To establish a causal effect between the two, the Chinese researchers used a genetic approach known as Mendelian randomization where they analysed genetic variants that influence both OCD and gut bacteria. They took two sets of samples, in one of which they assessed links between genetic data and gut bacteria in 18,340 people. In the second one, consisting of 199,169 people, they studied the connection between genetic data and OCD. the Mendelian randomization helped them bridge the gap and connect gut bacteria patterns with OCD.

The study found that the presence of one set of three bacteria protected against OCD, while another three upped the risk of OCD. Proteobacteria, Ruminococcaceae, and Bilophila fell in the first group, and Bacillales, Eubacterium, and Lachnospiraceae UCG001 were responsible for OCD. A link between gut and brain is not a new revelation. A past study found that low levels of Ruminococcaceae species could cause depression. "Future research should employ longitudinal designs and diverse populations to validate and expand upon these findings, as well as a more in-depth classification of microbes and their metabolic products, to further understand the role of gut microbiota in OCD," write the researchers.

Scientists are hopeful that the latest research on gut microbe and OCD could help treat the condition some day. However, that might be still far off into the future. The research was published in the Journal of Affective Disorders.