Mary came to see me because her anxiety was out of control. At thirty-five years old, she and her husband decided it was finally time to have a baby, but it just wasn’t happening. Difficulty getting pregnant was creating tension in her marriage, which left her either unable to go to sleep or waking up in the middle of the night feeling shaky and afraid. It had gotten so bad that, during the day, she was struggling to concentrate on tasks at work and at home.
Mary is not alone. Like many women her age, she was feeling the tension of having a full-time job and the pressure to have a family. Add in the stresses of a global pandemic and a host of other day-to-day fears, responsibilities, and frustrations, and it was easy to see how her anxiety could result from the accumulation of stresses in her life. But upon further examination, I noticed that something else might be at play.
As we spoke, I saw that she had a rash on both sides of her face, extending over both of her cheekbones in the shape of a butterfly’s wing. She thought she might be reacting to a new face cream and told me she’d booked a dermatology appointment, but I suspected something more serious. The clinical name for this rash pattern is a “butterfly rash,” and it is a telltale sign that a patient’s immune system is attacking their own tissues. A leading culprit, especially in women of childbearing age, is an autoimmune disease called systemic lupus erythematosus, commonly known as lupus. Patients afflicted with this condition may have inflammation of several organ systems: the kidneys, skin, joints, blood, and nervous system can all be affected.1 Although we don’t fully understand how or why lupus develops in individual cases, we do understand that many of these organ changes are caused by an immune response in overdrive. Recent research has shown that the composition of our gut bacteria can be a major factor in lupus patients.2 Stress and anxiety can disrupt the intestinal barrier, such that communication between the gut and brain breaks down. It’s the biological equivalent of spotty cell service, leading to dropped calls and texts that won’t go through as your communication falters. When this becomes chronic, a kind of metabolic confusion arises, which can contribute to the sort of abnormal immunity that can lead to conditions like lupus.3
Treating a complex disease like lupus is never an easy task. It’s a condition with no true cure, but through a variety of treatments and therapies, most patients can bring their symptoms under control. I referred Mary to a primary care physician who worked closely with a rheumatologist and put her on a course of steroids to reduce her inflammation. I prescribed her an initial course of an SSRI and a benzodiazepine, traditional treatments for anxiety. But I also had a conversation with her about making major changes to her diet to comprehensively address her anxiety. We took an inventory of the less-than-healthy habits she had picked up over the pandemic. She admitted she had developed a passion for bubble tea—delicious but full of sugar—which I encouraged her to replace with a healthier Matcha Green “Bubble” Tea (see here). I coached her on how to add a higher dose of anti-inflammatory foods to her diet, which would bring back biodiversity to her gut microbiome: different colors, textures, sizes, and shapes of vegetables such as peppers, zucchini, summer squash, Brussels sprouts, cauliflower, beets, and more. I recommended she replace her inflammation-producing vegetable oil with olive oil, increase her consumption of fermented foods like miso and kimchi, amp up her omega-3s by adding wild sockeye salmon and anchovies, and opt for hemp milk instead of dairy milk (see here for my Homemade Hemp Milk recipe). I will explain these specific recommendations later in the book, but the overall goal was to move her toward healthy whole foods and away from processed ingredients.
Mary had a good short-term response to the steroids, and the psychiatric medications helped somewhat, but when she came in for a follow-up visit, she was still struggling with both anxiety and her lupus symptoms. I asked her about the dietary changes, and she admitted that things had felt too hectic for her to change the way she ate in the middle of everything else going on in her life. I sympathized completely but encouraged her to start small and stay consistent, and I met with her and her husband to plan out meals, like Masala Baked Salmon (see here) and my Go-To Calm Green Salad (see here). She could prepare these ahead and use them on multiple days, making meal prep and planning easier.
Sure enough, once she committed to the dietary changes, we truly started to see shifts in her mood. Within just a month of consistently embracing an eating plan that was healthier for her gut and brain, she was feeling calmer and sleeping better. And as her anxiety waned, her lupus symptoms became easier to manage—a clear sign that her immune system function was improving. Mary couldn’t believe that her diet was playing such a central role in both her mental health and her autoimmune disease, but I explained that until recently, no one—from patients like her all the way to the highest echelons of medicine—knew about the vital interplay between our gut bacteria, the immune system, and anxiety.
What was really going on inside Mary’s body when she first came to see me? There were three major factors at play: her anxiety, which was centered in her brain; her gut microbiome, which was influenced by her diet; and her struggles with lupus, the result of disruptions in her immune system. It’s tempting to try to determine a root cause and connect her issues together in a defined sequence of events. For instance, we might theorize that her anxiety arose first, which then led to disruptions in her gut and eventually her immune system. Or we might suspect that her imbalanced gut microbiome led to her anxiety, which set off her immune issues. Or maybe her immune issues arose first, which in turn altered her gut microbiota, triggering her anxiety.
Truthfully, all of these scenarios are possible. There are no one-way streets here. These three body systems are interconnected in a delicately balanced ecosystem, and the variety and breadth of their interactions are mind-boggling. But, as we’ve touched on before, it’s important to realize that the primary cause does not matter. A disruption in any of these three systems is likely to lead to problems with the other two. Regardless of where the problem is rooted, the surest, most accessible, and easiest to control variable is the food you eat. As we saw with Mary, it wasn’t enough to treat just the anxiety or the lupus; it was also crucial to treat her gut microbiome through changes in her diet. Only by taking care of all three systems was she able to get her total health back on track.
Since we have already explored the gut-brain connection, let’s meet the immune system and learn about the mechanisms through which it influences your mental and digestive health—and vice versa.
It’s a dangerous world out there. Every living thing is constantly beset by a host of dangerous foreign invaders called pathogens. All organisms need defense mechanisms to protect against pathogens—or else they won’t be living for long.4
I’m sure you’re familiar with at least some of the work your immune system does. Everyone has been grateful for a “strong” immune system when that tickle in your throat fails to materialize into a cold or has lamented a “weak” immune system when you’ve gotten sick multiple times back-to-back. And during the rise of the COVID-19 pandemic, we all got a crash course in immunology from both a biological and epidemiological perspective, with talk of herd immunity, vaccine efficacy, and monoclonal antibodies. But despite knowing how important the immune system is, its actual mechanics can feel abstract and opaque. I want to demystify them here so that we’re well prepared to learn about how immunity interacts with the gut and brain.
The immune system keeps every part of your body under constant surveillance, which requires a nimble and flexible approach. It needs to be active in your skin, your respiratory passages, your intestinal tract, and anywhere else pathogens, cancer cells, and toxins might appear. Many of the organs important to immunity are part of the lymphatic system—for instance, your bone marrow, where key immune cells are made; your lymph nodes; and your thymus. But the immune system’s action isn’t limited to one organ system. Your skin, mucous membranes, and (you guessed it!) gut are also crucial.
There are two different types of immunity: innate immunity and adaptive immunity. They operate in complementary but different ways, stepping in to protect your body from different kinds of pathogens and utilizing different sets of chemicals and antibodies to do their work. Both are essential to your body’s ability to keep itself healthy.5 Though the immune system’s functions are complex enough to fill an entire book of their own, here’s a brief overview of how these two types of immunity work to protect you.
Innate immunity is your body’s first-line response to a foreign invader. It’s like the body’s paramedic team. When there is trouble, the innate immune system is ready to detect the problem and show up quickly on the scene with a trauma kit designed to handle emergencies. For instance, when you cut your finger, it is your innate immune system that rushes in to try to ensure that stray bacteria aren’t allowed to blossom into a full-blown infection. Speed is essential, given how quickly some pathogens can grow into a real threat. And since your body has no way of knowing what foreign invaders will try to intrude, the innate immune system must be prepared to thwart pathogens it has never seen before.
The innate immune system locates trouble by zeroing in on certain warning signs. Researchers call these warning signs pathogen-associated molecular patterns. Once trouble is detected, immune cells produce cytokines, small proteins that are crucial to your immune cells’ communication.6 Cytokines act as the paramedic team’s walkie-talkies, calling in reinforcements and making sure every responder is on the same page, part of a cohesive strategy to fight off the invaders.
Once trouble is detected and the right team has been assembled, the innate immune system can pull all kinds of different levers to slow down pathogens. It can create a more hostile environment for pathogens by altering the body’s pH or raising its temperature (which you may experience as a fever). It can recruit a variety of leukocytes, or white blood cells, which perform many different functions to destroy pathogens. For example, phagocytes like macrophages and neutrophils specialize in gobbling up pathogens, engulfing and destroying them. Natural killer cells are named for their innate toxicity to certain viruses and tumor cells.7 One of the main ways your immune system fights pathogens is by triggering inflammation, which brings leukocyte-rich blood to the problem area. As we saw with Mary at the beginning of the chapter, inflammation can be harmful as well as helpful—we will cover this in more detail in chapter 4.
The innate immune system uses a wealth of resources and strategies to act as a first line of defense against pathogens. But there is a trade-off: innate immunity does not have “memory.” While it is prepared to fight off pathogens your body has never seen before, it doesn’t “learn” anything from the experience. The next time your innate immune system sees that same pathogen, it will trigger the same response, whether or not it was effective the first time. Some pathogens are sophisticated enough to overwhelm the paramedics, and longer-term help is needed. Luckily, they can get on their cytokine walkie-talkies and call for reinforcements.
If the innate immune system is your body’s paramedic team, the adaptive immune system is an experienced group of medical researchers. They may not specialize in stopping bleeding or setting broken bones, but they excel at studying a disease inside and out, gradually building a body of knowledge to fight it more effectively and intelligently. While the innate immune system works from a standard tool set for different types of pathogens, the adaptive immune system builds a unique response for each pathogen and hones its approach with time and experience.
Adaptive immunity is called into action against a host of familiar infectious diseases. Take chicken pox, for example, a virus that eludes your innate immune system to create its characteristic blisters and itchy rash. But once you’ve been exposed, chicken pox is so effectively handled by your adaptive immune system that you’ll probably get it only once, during childhood. At least that’s how it was when I was young. Now that there is a vaccine available, many people don’t get chicken pox at all. Vaccines are another example of your adaptive immune system at work; they use weakened, inactive, or simulated versions of viruses to teach your adaptive immune system how to fight the pathogen more effectively. Think of the COVID-19 vaccine, which teaches the adaptive immune system how to deal with a serious novel pathogen, so vaccinated people get COVID at lower rates, and those who do get it have a much lower chance of serious symptoms.8
The adaptive immune system is called into action by the innate immune system through antigen-presenting cells. These cells—particularly dendritic cells, named for their branching structure—detect and identify antigens, a general term for small, harmful molecules of foreign substances that can trigger an immune response. When an antigen is detected, antigen-presenting cells activate T cells, a type of white blood cell that is a major player in adaptive immunity. When activated, T cells differentiate into helper T cells and killer T cells. Helper T cells offer support by secreting cytokines that coordinate the immune response in a variety of ways. Killer T cells destroy cells that have been corrupted. T cells are assisted by B cells, another type of white blood cell that is tasked with producing antibodies. Antibodies are proteins that bind to antigens, neutralizing threats and eliminating them from your body.
The signature of the adaptive immune system is that both T cells and B cells get better at their jobs with time. Each exposure they have to a particular pathogen sharpens their response, leading to a more effective defense the next time they fight it. Your body remembers which antibodies to produce for different antigens, so challenges to your immune system are much more easily met. And if your immune system doesn’t have to work as hard to protect you, it will be easier for you to feel your best. What might have been a debilitating illness the first time your body encounters it might be something you don’t even notice the next time you fight it off.
I want to emphasize that this is a bare-bones overview of the mechanics of your immune system. The field of immunology is extremely complex, and research continues to uncover new aspects. But just knowing the basics is enough to understand the ways in which your brain and gut can disrupt this intricate machine.
There are few things I love more than holding a newborn baby. It’s so incredible to imagine how what started as a mere zygote nine months before has become a living, breathing infant, so full of the beautiful potential to grow and develop all the incredibly complex systems that make up our bodies. In addition to marveling over tiny hands and feet, I can’t help but imagine the development of a fledgling gut microbiome.
While other major parts of the baby’s body would have developed during the mother’s pregnancy, the microbiome doesn’t have the same head start. Babies in utero are largely sterile, with the mother’s body keeping potentially harmful microbes far from a developing fetus (though there has been recent research indicating the presence of some bacteria in the placenta, umbilical cord, and amniotic fluid). Once the baby emerges into the world, however, there’s no such luxury—even a young infant needs the benefits of a friendly gut microbiome and a robust immune system to protect against invaders. Though the microbiome isn’t passed down genetically and doesn’t develop in the womb, a mother still has ways to help her new baby establish a colony of helpful bacteria.9
The first vector for helping a baby develop a microbiome is in the birth canal. As the baby passes through during a vaginal birth, the mother confers bacteria from her intestines and vagina; these bacteria form the basis of the microbiome. Premature babies and those delivered by C-section miss out on that initial transfer, resulting in less complex microbiomes than those of babies delivered vaginally at full term. This is a necessary trade-off, since C-sections are often essential for the health of mother and baby, and the difference in microbiome composition gradually recedes, with most babies having similar bacterial composition at around a year old. Still, adults who were delivered by C-section have been shown to have an increased risk of infections, allergies, and inflammatory disorders.10
There is an explosion of good bacteria in the first week of the baby’s life, facilitated by breastfeeding, which promotes a healthy microbiome and growing immunity through the transfer of antibodies.11 As different strains of bacteria proliferate, they spur the development of different features of the immune system. For example, in the first hours after birth, a baby’s microbiome largely consists of strains like Enterobacteriaceae that promote the development of natural killer cells and other types of T cells. In the first week of life, the vast increase in bacterial proliferation leads to the development of new types of leukocytes, like neutrophils and macrophages. In the following weeks, as strains like Firmicutes and Bacteroidetes take over, leukocytes mature and B cells develop. Finally, both systems gradually reach maturity at around two years old, but any disruption in that gut-immune development process can mean trouble later in life.12 The use of microbiome-disrupting antibiotics in childhood can lead to issues with antibodies and cytokines that lead to increased susceptibility to allergies and asthma.13 Certain differences in gut microbiome composition can lead to childhood disorders like type 1 diabetes14 and to long-term metabolic disorders like obesity, type 2 diabetes, and nonalcoholic fatty liver disease (we’ll learn more about metabolic disorders in chapter 6).15
I want to be clear that C-section delivery, formula feeding, and using antibiotics to fight serious infection during infancy are all important and valuable tools that help ensure that every baby can be born safely. Each mother’s situation is different. Our growing knowledge about the role of the gut microbiome in immune development isn’t a reason to discourage those practices, but rather a reason to develop new ways to mitigate the trade-offs as effectively as possible. Happily, ongoing research has shown real promise in the potential of probiotic treatments to help spur healthy microbiome and immune development in these cases.16
Even if your microbiome and immune system were healthy during their formation, that’s no guarantee that everything will continue to function perfectly. Throughout your whole life, your gut microbiota and your immune system will continue to work together and keep each other in balance, nowhere more crucially than in the gut mucosa.
While the immune system is active throughout the body, immune cells particularly like to hang out in the gut. In chapter 2, we learned that the gut contains the largest collection of nerve cells in the body; not to be outdone, 70–80 percent of your immune cells reside in your gut as well!17
That concentration of immune cells makes sense when you consider the challenge your gut faces every day. The food you eat is full of vital nutrients, but it can also carry dangerous pathogens—the kinds of harmful bacteria, viruses, and parasites that might lead to various forms of food poisoning, like norovirus, salmonella, staph, listeria, and botulism. The digestive process brings those potentially harmful invaders deep into your body, where they must be contained to keep from causing you harm. Your gut separates out the helpful nutrients while rejecting harmful bacteria and other pathogens, ideally neutralizing the threats and ejecting them as waste. But your gut can’t afford to be indiscriminate, rejecting all bacteria on sight. As we well know, to function properly the gut relies on massive colonies of helpful bacteria, which must be preserved even as harmful bacteria are destroyed. Separating the good bacteria from the bad bacteria is a tall order, and it’s possible only thanks to a huge variety of processes and methods of communication between your immune system and your gut.18
The nexus of immune action in the gut is the intestinal mucosa, a layer of mucus lined by epithelial cells, which provides a barrier between the potentially harmful contents of your gut and the rest of your body.19 If you look at a cross section of the small intestine, you’ll see a cylindrical tube that looks like a roll of paper towels. The layers of paper towel are the outer layers of the gut, made up mostly of different types of muscle that help your body squeeze food through your intestinal tract. The hollow middle of the tube, the intestinal lumen, is where most of your gut microbiota reside. The cardboard that makes up the walls of the tube is the intestinal mucosa. The immune system sets up shop in the mucosa, keeping a close eye to make sure no threats arise. In fact, in a healthy gut, all immune response takes place in the mucosa, because harmful bacteria are not able to penetrate through this protective layer into the rest of your body.20
When everything is functioning well and your gut health is properly balanced, with helpful bacteria protected and harmful bacteria contained, you have achieved gut homeostasis. But if you have an imbalance in your gut bacteria leading to an overgrowth of bad bacteria, or if something goes awry in your immune system, this crucial interaction in your gut mucosa can break down. The mucosa itself can physically degrade and become easier to penetrate, allowing harmful pathogens to slip through into the rest of your body. This is the dreaded leaky gut (more formally called intestinal permeability) that is increasingly recognized as an enemy of good mental and physical health.21 While we are only at the beginning of our understanding of the array of harm that can be caused by leaky gut, increased intestinal permeability has been linked with an increase in many different conditions, from gastric ulcers to food allergies to metabolic diseases like diabetes, autoimmune diseases like inflammatory bowel disease (IBD) and celiac, chronic inflammation, and cancer.22 As we’ll see in chapter 4, leaky gut is a key cause of increased inflammation throughout the body, another major factor in anxiety.
I want to emphasize that none of these interactions are taking place in a vacuum. As we discussed in chapter 2, gut dysbiosis can be fuel for anxiety on its own. And now we understand that gut dysbiosis can also drive immune disruption, which can trigger or worsen anxiety in other ways. In other words, any factor that upsets gut health or immune health is likely to upset mental health, too. It’s all connected.
For now, let’s turn our focus away from the gut to the rest of the body to see some direct links between mental health and immunity that illustrate how being anxious can make you sick, and how being sick can make you anxious.
My patient Eileen seemed happy. Everyone at work called her “Miss Sunshine.” Others would complain when things got busy and stressful, but Eileen kept on smiling. She smiled through everything at work and at home: her toxic boss, her unsupportive husband, and her overwhelming life. Even when she came to my office for help with her “work stress,” she was reluctant to drop the facade. It took several months to get her to open up about her overwhelm, but eventually she started to talk to me about how difficult things had truly been for her. When a big project came up at work, she was tasked with holding everything together, managing personalities and heavy workloads under tight deadlines. Those stressful periods were particularly challenging for her, but even between projects when work was quiet, she talked about how she was constantly full of dread, a feeling she tried to bury down deep. My suspicions were confirmed: Eileen was suffering from anxiety.
I began to help Eileen identify and understand the layers of her anxiety through therapy, trying to help her manage the busy periods and let go of her dread between projects. But even as she worked on her mental health, something else began to concern me. She started to lose weight, despite not trying to do so. Anxiety can cause some people to lose their appetite, but that hadn’t been the case for Eileen in the past. I encouraged her to get evaluated by her primary care doctor, who in turn referred her to a specialist. Before long, she was diagnosed with breast cancer.
As a cancer thriver myself, I understood the crushing weight of the diagnosis, but I also knew that Eileen had the resilience and strength necessary to regain her health. It made me reflect on how my experience with cancer helped me become more in tune with my spiritual practice and mindfulness and led me to the principles of nutritional psychiatry, which became the blueprint of my work today. Little did I know at that point that those practices of sound nutrition were also positively impacting my immunity.
Thankfully, as scary as it was, Eileen’s cancer was manageable, and she responded well to chemotherapy. After her recovery, she continued to embody a positive and upbeat attitude, but together we developed strategies to help her avoid suppressing her emotions to such a dramatic and destructive degree, and we made changes in her diet to help quell anxiety and support her immunity.
There’s no way to determine the direct cause of Eileen’s cancer. There are a host of factors involved in breast cancer, and any number of them could have been at play. But I have a hunch that Eileen’s mental health played a role in leaving her more susceptible to cancer. A 2019 review of fifty-one studies, encompassing a sample of 2,611,907 participants over a mean time period of more than ten years, established that people diagnosed with depression and/or anxiety were significantly more likely to get cancer, with higher rates of mortality from cancer as well.23
Regardless of whether Eileen’s personality traits contributed to her cancer, there is abundant evidence that our emotions can affect our immunity. For instance, an interesting cross-sectional study from 2022 showed that patients who suffered from mental illnesses like anxiety and depression had a higher risk of severe complications from COVID-19 than patients who had no such history.24
It doesn’t take a team of medical researchers to guess that you’re more likely to get sick when you are suffering from stress and anxiety, nor is it difficult to see why suffering from an illness might cause a strain on your mental health. We’ve all had those moments when our immune systems seem to break down at the worst moments, just as life is disrupted by major happenings at work or at home. But unlike a lot of folklore about susceptibility to illness—for instance, that being caught in the rain will lead to a cold, which my beloved grandma would tell me all the time—this one is actually true! And luckily for us, there are teams of medical researchers in the field of psychoneuroimmunology dedicated to understanding this very connection.
Eileen’s struggles with her mental health were rooted in two separate but related issues: stress and anxiety. As we discussed in chapter 1, the two conditions are tightly related, and they trigger the same response in your brain and body, but there are key distinctions between them. Stress is caused by an external trigger; in Eileen’s case it was the big work projects that she handled well on the surface but that took a toll on her mind and body. Stress can cause an array of symptoms in your brain and body, including irritability, upset stomach, and disrupted sleep. But ideally, when the source of the stress is removed, the symptoms disappear. Anxiety results in symptoms similar to those caused by stress, but as we discussed in chapter 1, it is rooted internally, persisting even when there is nothing concrete to be anxious about. Eileen’s stress was certainly feeding her anxiety, but even during easier periods at work she couldn’t feel calm; she was stuck in a state of constant dread that kept her body’s stress response firing no matter what was actually going on at work.
Remember that stress exerts its impact on the immune system via the CNS; the ANS, which controls our fight-or-flight response; and the HPA-axis. The HPA-axis regulates the release of crucial hormones, particularly the “stress hormone” cortisol, which spikes when your body is under acute stress to give you an extra jolt of energy. While cortisol and other similar hormones like epinephrine (also known as adrenaline) play an important role in keeping you safe from danger, too much of them can have a variety of negative effects, including weight gain, fatigue, and high blood pressure. They can also dysregulate the immune system, interfering with the production of various cytokines that help you respond to threats.25
I want to reiterate that hormones released in the stress response aren’t necessarily bad—without our ability to react strongly in stressful situations, I’m sure our species would have been considerably less successful! And there’s even some evidence that acute stress can actually stimulate the immune system. For example, studies have shown that short-term stress can enhance immune responses induced by vaccines and triggered by fighting tumors and recovering from surgery.26 Other studies have shown that acute stress enhances the function of immune cells in both innate and adaptive immune responses.27
But in other cases, even acute stress can be harmful to your immune system. For example, a decade-long study of medical students found that the students’ immunity went down every year under the simple stress of the three-day exam period. Test takers had fewer natural killer cells, they almost stopped producing the immunity-boosting cytokine gamma interferon, and their infection-fighting T cells showed a weaker than normal response. For stress of any significant duration—from a few days to a few months or years—all aspects of immunity went downhill.28
Treating Eileen helped me understand why it is so critical for anxiety sufferers to know a little more about these connections. While acute stress can have positive and negative effects, researchers agree that long-term stress is universally harmful to the immune system. A review of more than three hundred studies spanning thirty years found that chronic stress causes significant damage to nearly all measures of the immune system, including leukocyte counts, natural killer cell function, and cytokine production.29 This is because cortisol and other chemicals released by the stress response are not intended to linger in your system. They’re designed to give you a quick burst of energy to get you out of harm’s way, after which the threat should be averted and the stress response can dissipate. But if the stress response is not turned off—either because of continuous exposure to actual stressors or because anxiety is tricking your brain into anticipating stressors that have not appeared yet—your immune system begins to lose the ability to fight inflammation and coordinate and communicate to respond to threats.30 As a result, chronic stress has been linked with an elevated risk for numerous diseases, including infectious illnesses, cardiovascular disease, diabetes, certain cancers, and autoimmune disease, as well as general frailty and mortality.
Think back to Eileen. Before she came to see me, her cycle of stress and anxiety was never-ending. Even when she wasn’t in an especially stressful period at work, her anxiety ensured that her brain kept the flood of cortisol and other stress hormones flowing, giving her immune system no chance to recover. Therefore, it’s not surprising that anxiety disorders have also been specifically linked with this conflict between stress hormones, increased inflammation, and decreased immunity. For instance, one study found that people with GAD had imbalanced levels of crucial cytokines compared to the control group.31 Another study showed that patients with GAD were more likely to develop cardiac disease or have heart attacks.32 Other studies have suggested that GAD patients have reduced T cell activation compared to control groups.33
One of the clearest indications of the link between mental health and immunity is the incidence of autoimmune diseases in anxiety patients, just like we saw with Mary and her struggle with lupus at the beginning of the chapter. Autoimmune diseases are conditions where the body’s immune system attacks healthy cells as if they were pathogens. Like lupus, most autoimmune diseases are chronic with no definitive cure, though symptoms can often be managed through a treatment plan. In a variety of studies, autoimmune conditions like lupus, multiple sclerosis, and rheumatoid arthritis have been shown to correlate with serious mental health conditions, from schizophrenia to psychosis,34 and also more common conditions like stress and anxiety.35
While there is still much to learn about the connections between anxiety and immune disruption, we know enough to definitively say that this is yet another crucial link between mental health and whole-body health.
Now that you know more about the relationship between anxiety, your gut, and your immunity, I hope you can see the complexity of these problems and the difficulty of trying to pinpoint where things are going awry. But I want to emphasize again that it’s not necessary to know where the issues begin, because no matter what, the most powerful treatment in all these areas is the food you eat. A proper, healthy diet will always result in a healthy microbiome, which will always boost immunity and calm your mind.
As we’ve touched on throughout this chapter, one of the most destructive effects of disrupted immunity is increased inflammation. In the next chapter, we’ll focus on the dangers of chronic inflammation and how it is connected to anxiety.