Depressed? Anxious? Stressed? Don’t believe people when they tell you it’s all in your head. The truth is, it may be all in your gut.
As early as 100 years ago, scientists began investigating the connection between mood, the mind, and the digestive system. But it hasn’t been until very recently that the scientific community has started to take the link seriously.
That’s thanks, in large part, to a new understanding of the trillions of bacteria that inhabit the human digestive tract – collectively known as the microbiome. But even as recently as a couple of decades ago, mainstream researchers didn’t lend much credence to the idea that the microbiome had any connection to the brain.
Contrast that with the current state of affairs: In 2014, the National Institute of Mental Health pledged up to $4 million in grants to investigate the role of the gut microbiome in mental health disorders.
How the Microbiome Influences the Brain
As more research dollars are dedicated to the microbiome, scientists are finding more and more ways that this impressive collection of bacteria influences our health. So far, research has drawn clear lines between the microbiome and digestive conditions, immunity, metabolic diseases, allergies and more – including brain and mood disorders.
That last connection is especially intriguing. After all, it seems a bit far-fetched to think that bacteria in the intestines could influence anxiety, depression, and even perplexing problems like autism. But the evidence seems to point in that direction.
Scientists have even come up with a name for the symbiotic relationship between gut and mood. They call it “the gut-brain axis.”
Here’s how it may work. The bacteria in the gut are known to produce compounds that affect the brain. Those compounds – including dopamine, serotonin, and gamma-aminobutyric acid (GABA) – communicate, via the vagus nerve, with the parts of the brain responsible for emotions, including depression and anxiety.
From an evolutionary perspective, it makes sense. The microbes in our bodies have a vested interest in our social lives. After all, they can’t spread throughout the species if we are too depressed to leave our homes. So, it’s to their benefit to encourage positive, social behaviors in their hosts. That would explain the research that has shown that mice bred to have totally sterile intestines – meaning a fully depleted microbiome – display severely antisocial behaviors.
Mental Health Disorders and the Microbiome
Microbiome disruptions don’t have to be as extreme as the sterile gut example above to have real consequences. Here are just a few brain and mood issues that have been shown to be affected by bacterial balance:
- Depression and anxiety. Did you know that fecal samples of people with depression can be distinguished from those of non-depressed people? That’s because the balance of bacteria in the microbiome is altered in depressed individuals. Anxiety also has a gut connection. One study found that the probiotic (good bacteria) Bifidobacterium was more effective than pharmaceuticals in treating anxiety and depression in anxious mice.
- Stress response. A landmark study on mice found that when faced with a stressful situation, mice who had been fed the probiotic Lactobacillus rhamnosus were more relaxed and handled the stress better. These effects have since been replicated in human studies. In one, women who ate yogurt rich in probiotics twice daily responded better to stress-inducing images. Another study found that men taking the probiotic Bifidobacterium longumfor a month felt less stress than those taking placebo.
- It’s been clear for a while that autism has a gut component – 40 to 90 percent of children diagnosed with it suffer from some level of gastrointestinal distress. Research on mice has pointed to a possible reason – that mice with autism-like symptoms have abnormal microbiomes. Treating them with healthy microbes reduces their repetitive behaviors and communication difficulties.
While the research on the microbiome and the brain is promising, it’s still too soon to tell whether probiotics and other microbiome support will be the magic bullet for mood and mental disorders. It’s plausible, but more research on humans is needed before we can draw any firm conclusions.
Still, given all the other health benefits of a healthy microbiome, it’s a good idea to do what you can to take care of yours. The Eight Essentials, homeopathic formulas, and a microbiome-friendly diet, are great places to start.