In the 1800s, a French Canadian named Alexis St. Martin was shot in the stomach while at a fur trading post, when someone’s musket accidentally fired at close range. He survived, but his injuries resulted in a hole in his stomach wall. This provided an early window—literally—into how our emotions and mental health affect the gut. Through careful experiments, the surgeon William Beaumont
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Most people have experienced the gut consequences of their emotional feelings. Nerves before an exam might lead you to feel nauseous or even vomit. Profound sadness might make you lose your appetite, or perhaps cause a hunger impossible to satiate. Gut symptoms are common in mental health conditions, from appetite changes in depression to debilitating “psychosomatic” stomach pains. Many of our feelings are gut feelings.
But the gut doesn’t just respond to emotional feelings: it influences them, too. Take disgust. Disgust is visceral. Our stomach, like our heart, has a regular electrical rhythm; even just seeing something disgusting causes disruptions, called “dysrhythmias,” in this electrical signalling. Although disgust is crucial for survival—helping us avoid disease and stay alive—in many mental health conditions disgust becomes pathological. In obsessive compulsive disorder (OCD), for instance, dirt or germs can preoccupy someone’s thoughts, causing symptoms like compulsive hand-washing. Self-disgust is common in depression and eating disorders. And even post-traumatic disorder can be brought on by profoundly disgusting traumas.
Pathological disgust is particularly
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So gut feelings are not “all in your mind”—but they are not “all in your gut,” either. Sensations from the gut are transmitted to the brain via the vagus nerve, the primary channel of information sent from the body to the brain. A second route to target “gut feelings” is by electrically stimulating this nerve, which
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But the importance of the vagus nerve extends to even more established treatments: evidence from mice suggests that the most common type of antidepressant drugs (SSRIs, or selective serotonin reuptake inhibitors)
If the vagus nerve’s role helps us adapt to our bodily needs, perhaps the most important internal need of all is energy. One function of the gut—together with other organs—is metabolism, converting food to energy the body can use. There are mysterious and wide-ranging connections between our metabolic system and mental health. For example, the prevalence of depression in people with diabetes is
Our brain and wider nervous system adapts to its circumstances, including the body’s internal, metabolic needs, as well as our experience of the environment around us. Because of this, your gut-brain connection is not static, but rather changes and adapts over time. A
Gut feelings originate from many sources: directly through the gut, through channels of communication between gut and brain, or even through the brain itself. In neuroscience, as we unravel the dynamic communications between gut and brain, we can begin to understand how these processes helped our ancestors survive—and how we could better harness them to improve emotional and mental wellbeing. A gut feeling might have many possible causes, but each of these represent a potential solution for mental health.