Depression and Anxiety: Is the Answer in Your Stomach?

Susan James has floated an idea that sounds strange at first: some anxiety might start in the gut rather than the mind. She points to work by psychiatrist Dr. James Greenblatt, who once treated a teenage girl with severe obsessive-compulsive disorder and attention deficit hyperactivity disorder. On top of those symptoms, the girl had a long list of digestive complaints. What caught the doctor's attention was how badly she responded to psychotropic medication. That poor response made him look elsewhere.

Greenblatt ran a simple urine test for HPHPA, a metabolite produced by clostridia bacteria. Her levels came back high, which pointed toward trouble in her gut. He started her on strong probiotics to build up her beneficial bacteria, then followed with antibiotics. Over time the HPHPA readings fell sharply, in his words dramatically. Roughly six months later her digestive problems had cleared and her mental health had come back.

None of this comes from an alternative medicine practice. Greenblatt is trained in psychopharmacology and holds a clinical faculty post at Tufts Medical School. As he told ABC News, he leans on integrative medicine but keeps his prescription pad right next to him. He sits among a growing number of physicians who see connections between psychiatric symptoms and physical conditions, and who have begun paying close attention to what healthy gut bacteria can do.

The numbers are hard to picture. A typical adult carries as much as five pounds of bacteria in the digestive tract, trillions of individual microbes. James notes a study in the journal Science showing that lean people and heavier people host different bacterial populations, a finding that might eventually shape weight-loss approaches. She also mentions that doctors have turned to fecal transplants for elderly patients in nursing homes whose gastrointestinal health has broken down.

There is research behind the hunch. Studies point to a relationship between the bacteria living in the stomach and conditions like anxiety, schizophrenia, and autism. What sits in your gut, in other words, may shape what happens in your head. Work from The Great Plains Laboratory found that HPHPA runs much higher in the urine of autistic children, and that children treated with antibiotics targeting clostridia tend to see their symptoms ease.

A detail worth keeping in mind: babies arrive with a sterile digestive tract. They pick up their first bacteria passing through the birth canal, gather more from breast milk, and keep adding to the collection through ordinary contact with other people.

Greenblatt has treated hundreds of patients for dysbiosis, an imbalance of the microbes in or on the body. He argues that every patient should be tested for HPHPA before any psychotropic drug is prescribed. By his account, eight of ten people test fine. In the other two, elevated levels can hit the nervous system hard. He says he cannot understand why the test is not standard for every psychiatric patient, and that he questions its absence daily.

The chemistry he describes works like this. HPHPA shuts down an enzyme that normally converts dopamine into the neurotransmitter norepinephrine. With that conversion blocked, dopamine piles up. Too much dopamine can drive agitation, aggression, anxiety, and symptoms tied to schizophrenia.

A 2010 study at McMaster University in Canada, published in Communicative and Integrative Biology, tied intestinal microbiota to anxiety-like behavior. Co-author Jane, an associate professor of neuroscience and behavioral science connected to McMaster's Brain-Body Institute, calls the field well established, with two later studies backing up the original work. She explains that gut bacteria communicate with the brain through more than one channel, either the immune system or the enteric nervous system. Picture your intestinal tract wrapped around itself the way a bun wraps a hot dog, she says; more neurons cluster directly around the GI tract than fill the entire spinal cord.

Jane is careful about the limits. Probiotics may help a subset of patients, but she will not call them a magic bullet. Early-life stress, nutrition, and a well-built immune system all feed into mental health. Probiotics do help plenty of people, and the stomach-brain link can tighten during stretches like adolescence or menopause.

So a practical step emerges. If someone you care about struggles with mental health, it is fair to ask a doctor for a urine test to check for elevated HPHPA. A high reading might make that person a candidate for probiotics that address both the gut trouble and the psychiatric symptoms underneath it. Gut bacteria, the evidence suggests, can figure into whether mental health disorders take hold or stay away.