Why Is Everyone Complaining of Brain Fog? An Endocrinologist’s Perspective

Lisa, a nurse in her forties, once navigated the intricate demands of her ward with a mind like a finely tuned instrument. Now, she finds herself fumbling through routine tasks, her thoughts scattering like dropped papers, a cognitive fraying born from the confluence of perimenopause's hormonal shifts and the chronic sleep disruption of shift work. Contrast this with Val, a tech professional whose mind feels shrouded in "white static." Trapped in an "unreal present" sculpted by relentless information overload, she finds that following a simple conversation requires monumental effort—a tax levied by years of fractured attention across digital platforms. Though their stories seem worlds apart, Lisa and Val share the same unnerving symptom. Their experience reveals that "brain fog" is not a singular diagnosis but a final, common pathway where the deeply biological pressures of our bodies and the relentlessly technological demands of our world converge.

This feeling of a mind clouded and sluggish, a state patients have aptly named "brain fog," is becoming a defining complaint of our time. Google search data shows a dramatic, exponential increase in queries for the term since 2020. More concretely, data from the U.S. Census Bureau reveals a startling trend: since the pandemic began, there has been an estimated increase of one million working-age adults reporting "serious difficulty" with remembering, concentrating, or making decisions. This is not merely a post-viral curiosity or a consequence of stress. It is a physiological response to a world that has exceeded our biological design parameters—a world where our hormonal stress responses, our immune systems, and our very attention are under a constant, low-grade siege. We are living through a collective cognitive dimming, a slow-motion crisis that is forcing us to ask a fundamental question: what is happening to our minds?

As a physician, I can tell you that "brain fog" is not a formal medical diagnosis you will find in a textbook. It is a term that has arisen from the population itself, a grassroots description of a cluster of debilitating symptoms that defy easy categorization. Patients speak of a pervasive fatigue that sleep cannot touch. They describe a frustrating forgetfulness that erodes their confidence, and a mental confusion that feels like wading through mud. They talk about losing the thread of a conversation midway through a sentence or feeling "spaced out" and detached from reality. Neurologists, when they break down this experience, often characterize it as a disorder of executive function. This is the sophisticated set of mental abilities that allows us to plan, focus our attention, remember instructions, and juggle multiple tasks. The cruel irony of brain fog is that the memories are often still there, locked away in the mind's library, but the librarian—the executive system responsible for efficiently storing and retrieving them—has gone AWOL.

Indexed Google searches for ‘brain fog’. Credit: McWhirter L, Practical Neurology 2025

My own window into this phenomenon comes from my work as an endocrinologist. We specialize in the endocrine system, the body's intricate network of glands and hormones that quietly orchestrates everything from our metabolism to our mood. And this system, so often overlooked in conversations about cognition, is a critical player in the story of brain fog. At the center of it all is the Hypothalamic-Pituitary-Adrenal (HPA) axis, our body's command-and-control for stress. When we face prolonged physical or emotional duress—be it a traumatic event, a chronic illness, or the unrelenting pressure of modern life—this system can be pushed into a state of chronic maladaptive stress, which can affect hormone balance and signaling.

The thyroid gland, the master regulator of our metabolism, is another key culprit. It’s a common scenario in my clinic: a patient being treated for hypothyroidism with the standard medication, levothyroxine, has perfectly normal lab results for Thyroid-Stimulating Hormone (TSH), yet they continue to suffer. An estimated 10 to 20 percent of these patients experience significant residual symptoms, with brain fog chief among them. The issue may lie in a relative deficiency of T3, the more biologically active form of thyroid hormone, which standard therapy sometimes fails to adequately restore throughout the body's tissues.

Then there are the sex hormones. For women, the turbulent journey of perimenopause and menopause brings a steep decline in estrogen, a hormone that has profound effects on the brain. An estimated 60 percent of women experience some form of cognitive impairment during this transition, a fog that descends as their hormonal landscape shifts. For men, low testosterone is not just a matter of virility; it is closely linked to symptoms of fatigue, inertia, listlessness, and depression, which collectively manifest as a distinct form of mental fatigue. These delicate hormonal symphonies are being further disrupted by a modern world saturated with endocrine-disrupting chemicals and the ceaseless digital deluge. This digital deluge is not a benign distraction; it is a chronic, dopamine- and adrenaline-triggering stimulus, constantly prodding the very HPA axis we know can become exhausted, creating a feedback loop of hormonal dysregulation and cognitive fatigue.

From my clinical perspective, to attribute brain fog solely to hormones would be a mistake. Hormones are the conductors of the body's orchestra, but they are exquisitely sensitive to discord in other sections—especially the immune system. Pull on that hormonal thread, and you find it is knotted to the immune system. Pull on that, and you find it interwoven with our sleep cycles, our lifestyles, and most insidiously, the loneliness and digital architecture of our daily lives.

We are also seeing, with increasing frequency, brain fog as a hallmark of post-infectious syndromes. infections like Epstein-Barr, lyme, and now most notoriously, SARS-CoV-2 (COVID 19), can trigger a state of persistent immune activation. This chronic, low-grade inflammation unleashes a cascade of signaling molecules called proinflammatory cytokines. These are the same molecules that create "sickness behavior" when you have the flu—making you feel tired, cognitively slow, and unable to experience pleasure. In conditions like Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) or in autoimmune diseases such as Celiac disease and Multiple Sclerosis, this inflammatory state becomes chronic, and the brain fog never fully lifts. This state of chronic inflammation is further fueled by the modern condition itself. Chronic sleep deprivation, whether from insomnia or the circadian chaos of shift work, directly impairs attention, concentration, and memory. A diet high in refined carbs and processed foods creates its own inflammatory cascade through insulin resistance, starving the brain of stable energy. It's a physiological truth we often forget: heart health is brain health, and a lifestyle that neglects one will inevitably fog the other.

In my practice, I've noticed a profound shift over the last decade. Patients once came to me with fatigue primarily linked to clear metabolic or hormonal issues. Now, their fatigue is almost always entangled with a sense of profound digital and mental exhaustion. This is the digital fog of our own making, a phenomenon so pervasive it has earned the provocative moniker "brain rot," the 2024 Oxford Word of the Year. The relentless overconsumption of trivial online content is not a benign pastime. An abundance of academic research from institutions including Harvard, Oxford, and King's College London has found evidence that heavy internet use and multitasking are associated with a shrinking of grey matter in the brain's prefrontal regions. In parallel, a decade of data analyzed at Stanford University confirmed that this behavior correlates with reduced memory and attention spans. The average focus time on a single screen has plummeted from two and a half minutes in 2004 to just 47 seconds today. This relentless context-switching doesn't just shorten our focus; it makes the cognitive work of maintaining focus exponentially harder. This is the essence of "mental fatigue"—not a true depletion of energy, but a radical spike in the perception of effort for every task, a direct consequence of a brain rewired for constant, trivial novelty. Psychologic trauma can compound this, causing the brain's memory centers to go "offline" as a protective measure, making every single task, from answering an email to unloading the dishwasher, feel like a monumental undertaking.

If the causes are a tangled web, then the path to clarity must be a holistic one. It begins not with a magic pill or a detox protocol, but with the foundational pillars of health. Prioritizing a regular sleep-wake cycle is non-negotiable for cognitive restoration. Nourishing the brain with a balanced diet and proper hydration provides the raw materials for clear thought. And moving the body through moderate, consistent physical activity improves blood flow and supports neurological and functional health. Beyond these basics, we must actively work to restore our fractured attention. Attention Restorative Theory posits that we need to balance the effortful "directed attention" of our work lives with the gentle, restorative "involuntary attention" that comes from engaging in fascinating hobbies or spending time in nature and socializing with friends who value a similarly healthy lifestyle. We must also consciously manage our digital world, being mindful of screen time to push back against the tide of cognitive degradation.

If, despite these efforts, the fog persists and impairs your daily functioning, it is time to see a doctor. As an endocrinologist, my role is to untangle the physiological knots. We can investigate and treat underlying hormonal imbalances involving the thyroid, adrenal glands, or sex hormones. We also screen for common mimics and contributors to brain fog, such as deficiencies in iron, vitamin B12, or folate, which are surprisingly frequent and often go undiagnosed. A comprehensive evaluation is the necessary first step toward developing a targeted strategy to lift the haze.

What I have learned, both from the scientific literature and from the lived experiences of my patients—like Lisa and Val—is that the struggle with brain fog is a struggle to reclaim one's sense of self. Qualitative studies reveal that it can trigger a profound "crisis of identity," a distressing disconnect from the sharp, capable person they used to be. It is a disjunction between who they were and who they find themselves to be now, a state that can be deeply frightening. This condition, while real and complex, is not a life sentence. Understanding its multifaceted causes—from the hormonal to the environmental, from the viral to the digital—is the first, most powerful step toward taking control. The fog is thick, but it is not impenetrable. By addressing its roots with a comprehensive, compassionate, and informed approach, we can begin to find our way back to the clear, bright landscape of our own minds. Clarity is not a default state we have lost, but a deliberate practice of reclaiming our biology from a world that relentlessly seeks to fragment it.