OCD May Start in the Gut, Not the Brain, Surprising New Study Finds
Obsessive-compulsive disorder has long been considered a problem of the brain, but new research suggests the real driver might be hiding in the gut.
A team of scientists from Chongqing Medical University in China has uncovered a surprising link between gut bacteria and OCD, a chronic condition affecting up to 3 percent of people worldwide.
Their findings, published in the Journal of Affective Disorders, point to specific microbes in the digestive system that may help cause or prevent the disorder, redefining how we think about its origins and how it might one day be treated.
The researchers used a method called Mendelian randomization to connect the dots between genes, gut bacteria, and OCD. By analyzing data from over 217,000 people, they were able to isolate six types of gut bacteria linked to the condition.
Three—Bacillales, Eubacterium, and Lachnospiraceae UCG001—were associated with increased risk. The other three—Proteobacteria, Ruminococcaceae, and Bilophila—appeared to play a protective role.
“Specific gut microbiota might have a causal relationship with OCD,” the study authors wrote, noting this is the first research to strengthen the case for direct causality between bacteria and OCD rather than a mere association.
That distinction matters. Because genes are set at birth, this method helps rule out outside influences like diet or lifestyle, making it more likely that these microbes are directly involved in OCD development, not just bystanders.
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Some of these bacteria have been tied to mental health before. Low levels of Ruminococcaceae, for example, have also been observed in people with depression. Taken together, the findings underscore the profound impact of the gut-brain axis, an internal feedback loop that science is only beginning to fully comprehend.
OCD is often treated with a combination of cognitive behavioral therapy and SSRIs, but those approaches don’t work for everyone. In fact, 25 to 40 percent of patients see little or no benefit.
This new research hints at future therapies that may involve targeting gut bacteria instead of, or in addition to, brain chemistry.
“Despite the utilization of standard treatments, many patients experience suboptimal or no response,” the researchers noted. “The personal and societal toll of OCD is substantial.”
For now, the findings raise more questions than answers, but they open the door to a radical new understanding of one of mental health’s most stubborn disorders.
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