Depression may be a mental illness, but your body feels it, too—in your gut, under your skin, and even through your eyes.
Depression is the heavy blanket over a person’s mind that makes them feel hopeless, sad, and uninterested in the little joys in life. It messes with emotions and thoughts, which would lead you to believe depression is only about what's going on in your head. But is it?
One of the first patients I ever saw was a pleasant middle-aged man. His wife had made him go to therapy because she thought he was depressed. When he came in, the first thing he declared was, “I’m not depressed! I’m not sad—I’ve got no reason to be sad—and I don’t know why my wife thinks I’m depressed at all.”
At first, I took his word for it. He genuinely seemed to have no complaints about the state of his life, which was different from other depressed patients I had seen.
There was something very real, very physical, and very depressing in the room, and I felt it with my body.
But as the meeting progressed, I felt heavier and heavier. My body sunk into my chair. My gut felt like it was filled with lead. Later, my supervisor observed that even the pace of our conversation and slowed to a crawl. There was something very real, very physical, and very depressing in the room, and I felt it with my body.
Depression is a physical as well as mental illness
Our society has made major progress bringing depression, the common and debilitating disease, to public awareness. We've all heard about how depression affects our thoughts and emotions. It makes people less optimistic, more focused on negative experiences, and less interested in things they used to enjoy
What many still don’t realize is that depression is also a physical illness. It’s not “all in your head,” even though it’s called a “mental” illness. It is, in fact, in your head, and in your gut, under your skin, bound up in your body’s temperature, and even etched in your eyeballs.
What my patient didn’t realize was that depression could show up in various forms, not the least of which was in the form of physical changes in his body. It turned out that he was lethargic all the time, had trouble sleeping, constantly ached and tensed, and generally felt foggy. And it showed. By the end of our first meeting, the physicality of his depression had contagiously shown up in my body, too. That’s how I knew that his wife was right—he sure was depressed.
Don’t worry, he ended up doing very well in therapy. Over time, the light turned back on in his mind and body, and he said that it felt like the whole machinery of his body was creaking back into gear. I was reminded of him when brainstorming evidence-based facts about depression for this episode, and it inspired me to review the latest research on the physicality of depression. I want to share with you some surprising things I found about how depression is linked to the body.
Link #1: Depression is influenced by the bacteria in your gut
It might not seem obvious at first, but your brain and gut are two of the closest collaborators in your complicated body. They're connected by the vagus nerve, which is actually two bundles of nerves that serve as the information highway between the brain and the gut. They pass information in both directions about hormones, brain chemicals ... and the bacteria that play with our feelings.
That’s right—the bacteria in our gut influence our mood!
This relationship is very complicated, and scientists still don’t fully understand it. We do know that bacteria, of which there are 100 trillion in each of our guts, influences serotonin, an important neurochemical that plays an undeniable role in mood. We also know that stress in the womb and in infancy, which is a risk factor for later depression, causes changes to the gut microbiome. Animal studies have shown that giving depressed rats certain probiotics actually improved their depressive behaviors.
A lot more research is needed in this area before we can provide specific tips on how to improve your gut microbiome for better mental health. But I think it’s safe to say that a nutritious, varied diet is a good place to start. For example, there is evidence that the Mediterranean diet is good for a healthy gut microbiome, which may in turn benefit overall well-being. This is great news! Mediterranean food is not only delicious, but it may also be one of the Greeks’ secrets to happiness.
Link #2: A body with depression has a weird relationship with temperature
You know how it’s really nice to curl up under a blanket on the couch and have a hot cup of tea in the winter? Ahhh, it’s the little things in life!
This feels pleasant because there are heat-sensitive sensors in our skin that communicate with the brain, specifically to some of the brain areas involved in mood. When you wrap your hands around that hot mug, these areas of your brain light up. The more they do so, the more pleasure you feel.
People with depression have a less active thermoregulation system.
But people with depression have a weird relationship with temperature. In general, they have a less active thermoregulation system. They have higher core body temperatures and are less able to sweat, which is a major way that our bodies automatically regulate temperature. In the case of the hot mug in winter, those with depression have less of those brain responses to touching heat with their skin, so they’re not as able to get those little shots of joy.
Luckily, successful treatment of depression seems to restore the body’s normal ability to thermoregulate. There is also some evidence that we can directly use heat to treat depression.
A recent Journal of the American Medical Association (JAMA) study gave depressed participants just one session of whole-body heat treatment using infrared heat. The study showed that, even a whole week later, participants who received the heat treatment experienced less depressive symptoms than those who got a sham treatment without heat.
So, if you struggle with depression, one inexpensive way to give yourself some relief may be to take a hot bath or do some hot yoga.
Link #3: Depressed people feel more pain
When we say that depression is painful, we may be onto something more than metaphorical.
There has long been evidence that people with depression actually feel more pain. At least, they have a lower threshold for pain, meaning that it takes less pressure, heat, or other types of discomfort to cause a level of pain that feels unbearable.
For example, one recent study published in the Journal of Pain tested the pain perceptions of over 700 people that were actively in the middle of a depressive episode, as well as about 450 never-depressed control subjects. They induced pain through pressure to the index finger and found that the depressed individuals expressed pain at a lower pressure than their non-depressed peers. Statistically, they were able to relate this to the depressed group’s worse sleep and lower physical activity, both of which are common features of depression.
It’s difficult to say that getting better sleep (often not something a person can control) or increasing physical activity would help with pain perception. The study didn’t directly test this. But I'm willing to bet that better sleep and exercise wouldn’t hurt.
Link #4: Depressed people may literally not see as clearly
Depression is like a dark shadow that follows victims around, casting drabness over everything and making life look greyer and darker.It turns out that it may also literally make things look more blurry.
It turns out that depression may literally make things look more blurry.
One fascinating study by German scientists showed that, compared to non-depressed people, those with depression had less contrast sensitivity. Their eyes were less responsive to the contrast between light and dark blocks in a pattern. They measured the pattern electroretinogram (PERG), an objective indicator of the eyes’ response, in 40 depressed people and 40 healthy controls. Not only did they find that the depressed group had less contrast sensitivity, but the severity of depression mattered too—the higher someone’s depression score, the lower their contrast sensitivity. It’s hard to say why this is, and even harder to say whether we can do anything about it. Let’s stay tuned together on the research!
For now, know that depression is not only a mental phenomenon. It’s very real, and it’s very physical. For people who know they’re depressed, understanding these physical manifestations of the disease might help to find new ways of treating it, such as harnessing heat and diet to give the whole system a boost.
For those who don’t feel depressed, per se, but feel in their gut that something isn't right, it may be time to heed that gut feeling. It’s possible that your general feeling of foggy, achy, heaviness is not just due to the weather or midlife crisis—it could be depression making dents in the body.
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