OCD and the Gut-Brain Axis

Could Your Gut Flora Be Fueling OCD?

“Rule your mind or it will rule you.” —Horace

Obsessive-compulsive disorder (OCD) involves annoyingly recurrent thoughts and repetitive behaviors that can make your life miserable. It typically starts in adolescence and is often tied to stress and anxiety.

The gut-brain axis explains the astonishing connections between the microbes that live in your gut and your brain issues, including OCD. When your gut microbes are out of balance, your mood may suffer, and your OCD may worsen.

Studies since 2010 by researchers including Jane Foster, Karen-Anne McVey Neufeld, Gerard Clark, Ted Dinan, and John Cryan have found that gut microbes affect stress and OCD. The connection is largely a correlation, meaning it is not clear if microbe issues cause OCD or vice versa. The vice versa part is called reverse causality, and it is hard to rule out.

The mantra in biology is “correlation does not equal causation.” It is difficult to prove causation, but a new study from China aims to do just that, purporting to show that certain microbes cause OCD. The study, by Mingjie He, Jingfu Qiu, and colleagues from Chongqing Medical University, uses a newish technique called Mendelian Randomization (MR).

Mendelian Randomization shows causality

The idea of MR is to find genes that are associated with a specific trait. In this case, they found 88 genes associated with OCD. These genes are also associated with specific microbes in the gut, which are therefore also associated with OCD. At this point, you might be saying, “Great, now we have a more complex relationship, but it’s still an association.” However, the magic of MR is that while gut microbes may affect the brain, and the brain might affect the gut, none of these can affect the genes we got when we were born. In other words, reverse causality can be ruled out.

The study identified two sets of bacteria, one group protecting against OCD and another exacerbating it. For those keeping track of the players, Ruminococcus and Bilophila were the good guys, while Bacillales, Eubacterium ruminantium, and Lachnospiraceae were the bad guys.

The researchers conclude that specific gut microbes have a causal relationship with OCD, implying that dietary interventions might help prevent or treat the disorder.

Before we get too excited about the causality here, remember where we started: MR requires that we find genes that are associated with OCD, so some of the causality may be strictly genetic with no microbes involved. And these studies don’t always show the size of the effect. There are likely to be other factors involved. How much do those factors contribute?

New options for OCD

Current treatment for OCD includes psychotherapy and antidepressants, which often have impressive results. But some people are resistant to these treatments or desire a more natural approach. Knowing that microbes are involved, does that mean there might be dietary interventions that could help?

One dietary clue is the protective effect of Bilophila. The name gives this microbe’s affinity away: it means bile lover. Bile is produced by the liver to help digest fats. It is not uncommon for people with OCD to avoid meat, so they may have lower levels of both fat and Bilophila as a result. But fat is important to brain health, which is basically a fat pudding; some two-thirds of the brain is fat!

The best fat for the brain is omega-3, which can be found in fish, including salmon and sardines. These are great items to include in your diet, but if you have an aversion to eating animals, you can also find omega-3 fats in walnuts, flax, and chia.

Otherwise, if antidepressants can improve OCD symptoms, then a diet that mimics antidepressants may help. The dietary trick here is to increase fiber consumption, which feeds the healthy protective microbes. Those microbes then produce substances like butyrate that help to lower inflammation and encourage the growth of new nerve cells in the brain. Also, fermented foods like yogurt, sauerkraut, kimchi, or kombucha contribute to a healthy gut environment. There are few good studies on specific diets for OCD, but this is a good start.

Although there can be many other factors involved with OCD, it can’t hurt to improve your gut health, which lowers inflammation and improves cognitive function. If you have OCD, talk to your doctor about adopting something like the Mediterranean diet. It can be tricky to adopt a new diet for anyone; OCD doesn’t help. But it becomes easier with time, so don’t give up!

If you know anyone with OCD, pass this on. Life can be so much better!

References

He, Mingjie, Hongyang Zhang, Zheng Luo, Xinhao Duan, Feng Zhao, Peng Su, Zhijun Zeng, Lixiao Zhou, Chengzhi Chen, and Jingfu Qiu. “Causal Link between Gut Microbiota and Obsessive-Compulsive Disorder: A Two-Sample Mendelian Randomization Analysis.” Journal of Affective Disorders 379 (June 15, 2025): 852–60.

Foster, Jane A., and Karen-Anne McVey Neufeld. “Gut–Brain Axis: How the Microbiome Influences Anxiety and Depression.” Trends in Neurosciences 36, no. 5 (May 1, 2013): 305–12.