Medically reviewed by Tracy McCarthy, MD — Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner A Number Worth Sitting With Approximately 90 percent of the body's serotonin is produced in the gut, not in the brain. This single fact reframes the dominant model of depression - a model built on the assumption that mood disorders are primarily disorders of brain chemistry in ways that the research is still fully catching up to. If most of the body's seroto

The Question That Often Goes Unasked You have been working on your thoughts in therapy. You have been managing your stress. You have built better routines. And yet the irritability still spikes. The anxiety still arrives at predictable times. The low mood still settles in for days without a clear emotional trigger. What if the question is not what you are thinking or what you are avoiding, but what your body is doing? Mood is not generated purely in the mind. It is generated

A Model That Was Incomplete For several decades, the dominant explanation of depression was neurochemical: not enough serotonin, dopamine, or norepinephrine in the space between brain cells. The treatments that followed from this model were logically consistent — medications designed to increase the availability of these neurotransmitters in the brain. The model was not wrong. It was incomplete. A substantial and growing body of research now points to the immune system — spec

It Is Not in Your Head Every year around the same time, something shifts. The days get shorter. The light changes quality. And a heaviness settles in lower energy, more difficulty waking in the morning, a pull toward withdrawal, a mood that is harder to access or lift. You may dismiss it as busyness or attribute it to stress. You may tell yourself to push through. There is a biological explanation for what you are noticing. And understanding it does not mean pathologizing the

When the Standard Answer Has Not Been Enough You have tried medication. Maybe it helped partially. Maybe it did not help at all. Maybe the side effects made staying on it too difficult. You have been in therapy, and it has given you useful tools but something underneath still feels off. A heaviness. A flatness. An inability to feel quite like yourself that does not seem to be about your circumstances or your thoughts. If this resonates, I want to offer you something that conv

Something Has Actually Shifted You are eating roughly the way you always have. Your activity level is similar. And yet your body is responding differently. Energy is less predictable. Weight distribution has changed. Blood sugar feels less stable. Recovery from a disrupted week takes longer than it used to. This is not imagination, and it is not simply aging. These are measurable physiological changes that begin to accelerate in the fifth decade of life — particularly for wom

When the Explanation Does Not Fit the Experience You have had scans. You have had physical exams. You have been told there is nothing structurally wrong, or that what is there does not explain the degree of pain you are living with. Maybe you have been given medication that helped a little. Maybe you have been told the pain is in your head. Maybe you have simply been told to manage it. What you may not have been told is that chronic pain, particularly pain that is widespread,

Aging Is Not Simply About Time Passing Two people can be exactly the same age and have meaningfully different biological ages. Their energy, mental clarity, hormonal balance, and inflammatory markers may tell completely different stories. What separates them is not only genetics or luck. Increasingly, the research points to one underlying mechanism as one of the most powerful determinants of how we age: chronic low-grade inflammation. This is not the inflammation you notice w

When the Explanation Does Not Match the Experience You are in your early to mid-forties. You are sleeping poorly in ways that feel different from before. Your anxiety has shifted, less tied to circumstances, more like a low hum that will not quiet down. Your concentration is unreliable in ways you did not expect. You feel, in some hard-to-articulate way, less like yourself. You mention this to your doctor. You are told it is hormonal. You are given a prescription or told to w

The Missing Piece in Many Hormonal Conversations If you've been told your hormones are "normal" but your mood, cycle, or energy don't reflect that or if hormonal treatments have produced only partial improvement, there may be an environmental dimension to the picture that hasn't been examined. A growing body of research suggests that certain common environmental chemicals can interfere with hormone signaling in ways that produce symptoms indistinguishable from hormone deficie

Beyond the Cleanse When most people hear "detox," they picture a juice fast or a supplement kit. What actually runs detoxification in the human body is not a product. It is an organ - the liver and it operates continuously through two distinct biochemical phases that require specific nutritional inputs to function well. Understanding this is not a wellness concept. It is basic physiology with direct relevance to how you feel: your energy, your mood, your hormonal balance, and

Why Symptoms Sometimes Appear Without Warning Patients often ask me why their symptoms began when they did. Nothing dramatically changed. They didn't suddenly develop a new illness. Life was stressful, but it had been stressful before. And yet something shifted — and suddenly they were exhausted, reactive, foggy, or anxious in ways that hadn't been true a year earlier. The concept of total toxic load sometimes described clinically as the "toxic bucket" offers one useful frame

Medically reviewed by Tracy McCarthy, MD — Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner A Symptom Most People Attribute to Something Else If you've ever noticed that your vision seems slightly blurry or unfocused after a large meal or that it shifts at certain times of day without an obvious reason, you may have dismissed it as tiredness or screen fatigue. It may be worth considering another possibility. Blood sugar fluctuations have a direct a

Cravings Are Not a Character Flaw If you've spent time trying to override sugar cravings through discipline alone, you know how exhausting that approach is and how unreliable. What most people aren't told is that cravings are often physiological signals, not evidence of poor self-control. In functional medicine, we treat cravings as data. They are the body's way of communicating about blood sugar, stress hormones, nutritional status, and the gut microbiome. When we investigat

Medically reviewed by Tracy McCarthy, MD — Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner The One Most People Overlook If you track your sleep, manage your stress, eat reasonably well and still experience mid-morning brain fog, afternoon energy crashes, or a vague sense of anxiety on certain days, there is one variable that consistently gets overlooked: hydration. This isn't about drinking more water as a wellness platitude. There is a specific p

Medically reviewed by Tracy McCarthy, MD - Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner The Anxiety That Comes Out of Nowhere You weren't particularly worried about anything. The meeting went fine. And yet there it is a racing heart, a low hum of dread, that feeling of being vaguely on edge with no clear reason. For many of the patients I work with, this pattern has a physiological explanation that has nothing to do with their thoughts. It has

Medically reviewed by Tracy McCarthy, MD — Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner The Field Is Moving Fast Microbiome science is one of the most rapidly evolving areas in medicine. What was theoretical a decade ago is now documented with increasing precision — the specific bacterial signatures associated with depression, the mechanisms by which gut bacteria communicate with the brain, the ways in which diet shapes microbial populations in

Medically reviewed by Tracy McCarthy, MD — Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner Your Microbiome Keeps Time Most people know they have a circadian rhythm — the internal biological clock that governs sleep, wakefulness, hormone release, and metabolism. What is less widely understood is that the gut microbiome has its own circadian rhythm, running in coordination with the host's clock. Disrupting it has measurable consequences for metaboli

Medically reviewed by Tracy McCarthy, MD — Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner Diversity Is the Goal When researchers look at microbiome health, one of the most consistent findings is that diversity matters. A microbiome with a wide variety of bacterial species is more resilient, more functional, and more protective than one with a narrow population — even if that narrow population contains some "good" bacteria. 1. Eating a Low-Variety

Medically reviewed by Tracy McCarthy, MD — Board-Certified Psychiatrist, IFM-Certified Functional Medicine Practitioner You Are Not Alone in Your Body Inside your gut live trillions of bacteria, fungi, viruses, and other microorganisms collectively called the microbiome. The vast majority live in your large intestine, and the vast majority of them are working for you — helping digest food, regulate immunity, produce neurotransmitters, metabolize hormones, and communicate cons