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The Surprising Science of How We "Catch" Mental Illness
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Is it possible to catch autism or OCD the same way we catch the flu? Can a child’s contact with cat litter lead to schizophrenia? In her eye-opening new book, National Book Critics Circle Award-winning author Harriet Washington reveals that we can in fact “catch” mental illness. In Infectious Madness, Washington presents the new germ theory, which posits not only that many instances of Alzheimer’s, OCD, and schizophrenia are caused by viruses, prions, and bacteria, but also that with antibiotics, vaccinations, and other strategies, these cases can be easily prevented or treated.
Packed with cutting-edge research and tantalizing mysteries, Infectious Madness is rich in science, characters, and practical advice on how to protect yourself and your children from exposure to infectious threats that could sabotage your mental and physical health.
Table of Contents
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Gazing into the night sky with its seemingly numberless stars evokes our sense of infinity, but if you seek the ultimate multitude, look closer to home. What lies at our feet and within us dwarfs the heavenly spectacle, yet we need our imaginations—or a powerful microscope—to see it: microscopic bugs, not stars, dominate the galaxies. The earth alone holds five million times more microbes than there are suns in the universe. It is home to five nonillion infinitesimal beings—that's a 5 followed by 30 zeros.
Five million bacteria teem in every teaspoonful of seawater, accompanied by fifty million viruses. This makes viruses the most common life form in the seas, and no wonder: viruses infect most other living organisms, including bacteria.
Microbes do more than infect us, however; they are us, in the sense that we harbor more microbes than human cells. Your intestines alone provide a home for one hundred trillion viruses, fungi, protozoans, and—mostly—bacteria. These single-celled guests outnumber your cells ten to one.
Microbes thickly coat our skin, eyes, and genitals and cover the surfaces of our mouths; they specialize in specific areas of the body. Staphylococci colonize the skin, and lactobacilli coat the vagina. And that's just on the surface; ten thousand different species of organisms thickly populate your gut. Just as our genes make up our genomes, these microbial fellow travelers make up our microbiomes, which constantly adjust in type and numbers on different sites on the body and different sites on the globe.
And our health, including our mental health, changes with them.
Your microbiome has an astonishing power to keep you healthy—or ill. From the beginning, internal microbes guide your immune system's development. Your gut also possesses its own "brain." It houses a network, dubbed the enteric nervous system, or ENS, that contains a thousand times more neurons than your brain does. Its weight is twice that of your brain and it sends neurotransmitters that help direct your brain's activities.
During birth we acquire microbes from our mothers that confer immunity and may dictate our future health, from struggles with weight to a propensity to schizophrenia. As we grow, we acquire more pathogens and beneficial microbial "friends" that tip our odds of developing or avoiding everything from ulcers to heart disease to cervical cancer to obsessive-compulsive disorder.
The relationship between disease and microbes was first proposed in the seventeenth century, but the evidence and basic standards for the proof of infectious-disease causation weren't laid down until 1883, when the German bacteriologists Robert Koch and Friedrich Loeffler provided the first evidence that tiny, invisible microbes enter the body and cause diseases; this is germ theory.
The microscope enabled scientists to see the pathogens, document them, and, in doing so, disprove popular beliefs, such as that sinful behavior invites illness or that poisonous vapors called miasmas cause disease.
The uncontrollable dancing movements of St. Anthony's fire, once ascribed to satanic influence, are now known to result from Claviceps purpurea, a fungus that infects rye. Malaria is now known to be caused not by bad air but by a single-celled plasmodium, a parasite of the female Anopheles mosquito.
Contemporary researchers on five continents continue to unmask microbial roots of illness, and they now recognize that events as seemingly trivial as a sore throat or a case of measles—or even the flu—can breed anorexia, Tourette's, obsessive-compulsive disorder, or schizophrenia. Researchers in the field estimate that infectious organisms cause from 10 percent to 75 percent of some serious mental disorders.
In 1997, I glimpsed the extent to which mental illnesses are connected to infection when I happened upon an Italian medical-journal article that linked schizophrenia to bornavirus, which causes a fatal encephalitis in Central European sheep and horses. It asked whether humans acquire the virus from horses and whether such infections can cause schizophrenia. The article found a strong correlation between infection and illness, but no proof. Thus, it was inconclusive, and so were subsequent studies, as I learned when I called the investigators.
I was disappointed, but my curiosity was piqued as I searched for evidence of causal connections between infection and mental illness. I quickly found them, but many were lodged in the past. General paresis, cases of which once filled one of every five New York City asylum beds, is caused by a familiar disease: syphilis. When scientists discovered that penicillin cured syphilis, they also discovered a cure for this common mental disease. Now one must travel to the developing world to see a case.
In 1997, I learned of Paul Ewald, a visionary evolutionary biologist whose work describes a second wave of germ theory. He has elegantly argued for the unperceived importance of infection as an explanation of much human disease. Bacteria, viruses, fungi, and other infectious agents are responsible for many of the illnesses that we have long ascribed to genetics, behaviors, and even personality types. Cervical cancer, for example, was long chalked up to sexual immoderation but is now known to be triggered by certain strains of the human papillomavirus, just as the hepatitis C virus causes hepatitis C. Ninety percent of ulcers, which were long attributed to unmanaged stress and treated with milk, antacids, and the acid-lowering drug Tagamet, are actually caused by a bacterium, Helicobacter pylori, although stress may impair an ulcer's healing. Many heart attacks, long ascribed to aggressive, hostile, type A personalities, are now recognized as the legacy of the bacterium Chlamydophila pneumoniae as well as various gut bacteria.
In 1997 I also discovered the work of Dr. Susan Swedo, who proposed an intriguing syndrome fingering Group A streptococcal bacteria, or GAS bacteria, as the culprit in children who developed symptoms of anorexia, obsessive-compulsive disorder, or Tourette's in the wake of strep throats. She was actively seeking proof and a mechanism in human studies with scores of adolescents, many of whom had been brought to her clinics at the National Institute of Mental Health by their worried parents. I reported on these exciting developments in Psychology Today, but aside from Swedo's fledgling human studies, I found little contemporary evidence, just tantalizing correlations between infections and madness.
I periodically looked into the state of research linking microbes and mental disorders, and in 2013, I realized that it was burgeoning. With the acknowledgment of epigenetics, scientists moved away from exclusively genetic models of disease, including mental disease, and this made it easier to contemplate microbial causes and risk factors.
The pioneering research of scientists like Michael Gershon and Martin J. Blaser laid the groundwork for an emphasis on gut microbes that resulted in 2008's Human Microbiome Project, a $115 million enterprise that sought to discern the microbial causes of health and illnesses, including depression, autism, and obesity.
Since the early 1970s, when Freud's theories of mental illness were ascendant, prescient scientists like E. Fuller Torrey, director of the Stanley Medical Research Institute, and Robert Yolken, of Johns Hopkins, had rejected the belief that schizophrenia and other psychoses were exclusively the result of social and psychological dynamics. Instead, they had looked for answers in biology, specifically in microbial assaults on the immune and nervous systems. By 2013, mental-illness researchers had largely abandoned Freud to join the duo in exploring neurophysiology.
As a result of this sea change in research directions, we are approaching critical mass: a paradigm shift that replaces psychosocial factors with biological ones as the cause of mental illness. Most (not all) involved researchers think that microbes constitute just one risk factor; genetics, stress, psychological factors, and social dynamics are still important. In fact, most experts who hazard an informed guess about their relative importance suggest that infections cause 10 to 15 percent of mental disease. That may sound like a small number at first, but it is quite significant, especially when we consider, within that statistic, the many lives lost through suicide or early death and the even greater number of lives lost to profound disability.
Moreover, Yolken reminds us that immense numbers of mentally ill in poor and developing nations go undiagnosed, and we are not even aware of a greater number of microbes that undoubtedly exist in such areas; it is a mathematical certainty that some of them pose mental-health threats.
This book traces the growing evidence of microbial triggers of mental disease in infants, adolescents, adults, and people in the developing world. In describing the infinite variety of pathogenic mental disorders, it also interrogates the nature of proof, as opposed to mere correlation, and proposes that traditional mechanisms for establishing proof must be supplemented by modern tools and strategies. It examines the equally outmoded and simplistic notion of the "war" between man and his microbial hangers-on and suggests that our seek-and-destroy approach to pathogen control must be replaced by more nuanced strategies; we are involved in a chess game, not a brute battle to the death.
This book urges readers to employ the reasoning scientists have applied to physical illness to microbial mental illness. I'll show through historical examples that we have been loath to follow the facts that establish microbial causes and that our biases and antiquated habits of thought have resulted in our clinging to scientifically untenable and ineffective theories and treatments that have cost many their sanity and their lives.
Not only do microbes play a surprising role in our tastes and preferences—some acquired tastes seem related to our microbial exposure, as I'll explore—they also shape our societies. Infectious Madness discusses research demonstrating how microbes influence our collective behavior, shedding light on issues that go far beyond individual mental health. It looks at how the poor and medically underserved suffer far worse mental health than the rest of the population, in part because neither their pathogens nor their mental ailments receive appropriate scientific treatment. As it turns out, microbes shed light on some of the most mysterious and vital questions we face: Why are some societies more xenophobic than others? Why do some peoples tolerate or even encourage stranger violence, such as lynching, the Holocaust, or ethnic genocide in Bosnia and Rwanda?
In short, Infectious Madness endeavors to relate through the prescient work of visionary scientists how microbes rule not only the world, but also our minds.
Germ Theory Redux: The Acquisition of Mental Illness
A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it.
"When I was a student in the 1960s, I once saw a man in the final stage of syphilis," recalls English writer John Cornwell. "He was a patient on a psychiatric ward in London where I was working. White-haired, olive-skinned, emaciated, without a name or known country of origin, he had been picked up from a gutter in the London docks."
The man lived in a state hospital for the mentally ill, where he was cared for by a kind but resigned staff. "He stood all day in the corridor leaning against the wall, doing a slow-motion foot shuffle." The man, Cornwell tells us, was more than psychologically impaired. He could not hear or speak and seemed oblivious to his surroundings. "The ward charge nurse assured me that he was 'unlucky, the last of his kind.' He had not been given treatment in time to halt the final devastation of the disease."1
Cornwell's account reminded me of a patient I had encountered while working in an upstate New York county hospital in the 1960s. He was probably in his early sixties, but he looked younger, thanks to his vacant gaze and unfurrowed brow. Dressed in khaki pants and a T-shirt,2 he was gently propped in front of a peeling greenish wall every day, and he remained there, a slight smile playing about his lips, his equanimity undisturbed by the chaos and noise of the behavioral renegades with whom he shared the dayroom. Once, he was placed too close to the naked bulb of a torchère lamp whose shade had been lost in some forgotten drama, but when a staff member moved it to a safe distance, he neither averted his eyes nor tracked the aggressive glare. He was blind. He was also deaf, unable to speak or communicate, and he showed no signs of being able to reason or remember. He was reduced to someone who ate and defecated, who was bathed and dressed and shuffled along to nowhere with utter indifference. No one ever visited him.
What had happened to this man? The aide shepherding him to dinner whispered, "He's got paresis, and it has destroyed his brain. It's an old disease, you never see it now. He was treated with penicillin, but they can't bring back the lost function."
Lost. I hung on the adjective, which seemed to capture his condition so perfectly. Then I did a double take. "Penicillin? An antibiotic? For a severe mental disorder?" The aide shrugged as she and her charge moved on.
The antibiotic was in order because general paresis, a form of neurosyphilis, is seen in the late stages of syphilis and can emerge twenty to thirty years after the initial infection. Because it attacks in a very nonspecific manner, the neurosyphilis infection can appear in many different ways and damage many different areas of the brain. Whatever region comes under fire by the bacteria and their antibodies determines the disease's signs and symptoms, which are legion. In both Cornwell's patient and in the upstate New York man I observed, aural and visual systems had been destroyed and motor functions reduced to stereotyped residual movements. This damage can cause delusions, hallucinations, a diminished ability to think or speak, personality changes, impaired judgment, anger, irritability, and a sad or depressed mood. Both short-term and long-term memory may eventually disappear. There are physical consequences too, including changes in the pupil of the eye, overactive reflexes, sharp pains, a slow degeneration of the neurons' ability to transmit messages (somewhat like that seen in multiple sclerosis), and profound muscle weakness, all of which eventually relegate paresis sufferers to bed.
The New York man was treated in a general hospital, but the man with paresis whom Cornwell encountered in England was being treated by psychiatrists in a mental institution, as befitted his profound dementia and psychological and mental losses.3 If one had to choose between the two labels, this clearly was mental illness. Or was it? Given that a paresis patient is dogged by the loss of control over his movements, loss of vision, and other physical problems, and given that all this carnage resulted from a bacterial infection, was this not a physical disorder? For that matter, does one have to choose?
"There may be said to be two classes of people in the world," mused Algonquin Round Table habitué Robert Benchley in 1920, "those who constantly divide the people of the world into two classes, and those who do not."4 Physicians belong to the first group. They embrace the long-standing mind-body dualism that insists that mental disorders solely affect the mind, and physical disorders are the product of distorted physiology.
The fact that psychiatric diseases are now routinely located in brain dysfunction doesn't resolve the issue, because this acknowledgment doesn't necessarily represent a dissolution of the imaginary boundary between the physical and the mental. Instead, this stance often entails a belief in two distinct species of "mind." In one, consciousness and mental disorders are created by and dependent on the functioning of the brain, a sort of ghostly extension of the brain into psychic space. The other mind is viewed as completely separate from the brain. But without a specific indication of precisely which mind is meant, the scientific literature is often maddeningly fuzzy and unhelpful.
To what extent is automatically ascribing mental disease to psychological trauma and genetic determinism and physical disease to tangible environmental causes just a lazy habit of thought?
For ancient Greeks, the distinction between psychological and medical illness was not the most salient or definitive characteristic of disorders. In Hippocrates's disease taxonomy, mania, melancholia, and hysteria were treated with the same humoral-imbalance corrections that he prescribed for physical illnesses.
At the other extreme, there's a long history of attributing psychosis to moral failure. In Deuteronomy 28:27–29, rebellious Israelites were threatened with insanity. "The Lord will smite you with madness, blindness and with bewilderment of heart," it promises. Medieval scholars and theologians believed madness was spiritually induced, either by a failure of faith or by a punishment from the gods, a theory that died hard and that, arguably, persists in pockets of fundamentalism and faith healers.
However, by the time of the Renaissance, physicians and other Western medical experts placed mental diseases firmly in the fold of physical ailments and treated them as such.5 This view persisted for centuries. "From the Renaissance until the second half of the 18th century," wrote R. E. Kendell in the British Journal of Psychiatry, "melancholia and other forms of insanity were generally regarded as bodily illnesses not differing in any fundamental ways from other diseases." Even the famous psychiatrist Karl Menninger hypothesized in 1922 that schizophrenia was "in most instances the byproduct of viral encephalitis." And although it seems counterintuitive to suggest that humans can catch depression or schizophrenia in the same way we catch the flu, this hypothesis springs from germ theory, developed by Louis Pasteur in the 1860s and Robert Koch in the 1870s, which posits that specific microbes such as bacteria, viruses, and prions (infectious proteins) cause illness.6
Although most people think only of physical illness, not mental disease, when they think of germ theory, pioneering psychiatrists like E. Fuller Torrey, the executive director of the Stanley Medical Research Institute (SMRI), have sought to change this. Torrey has long rejected the relegation of mental disease to psychological causes alone and has spent the last half a century tracing the relationship between infection and mental illness.
In the 1990s, Torrey observed that in the late nineteenth century, schizophrenia and bipolar disorder went from being rare diseases to relatively common ones. During the same period he noticed that owning cats as pets replaced regarding them as Satan's minions, relegating them to barns for rodent control, and burning them to celebrate important holidays.
Around the time that England's first cat show was held at the Crystal Palace, in 1871, cat ownership became popular in America. That same year brought a sharp rise in U.S. schizophrenia rates7 (except among rural Hutterites, who "almost never" keep cats as pets). Cats carry a zoonotic infection (a disease humans acquire from animals) that causes schizophrenia.
In this case, Torrey suspected Toxoplasma gondii, an infectious single-celled organism discovered in 1908 by Charles Nicolle and Louis Manceaux of Paris's Institut Pasteur. The parasite lives in the tissues of many warm-blooded animals, but it can reproduce only within the stomachs of felids (domestic cats and other members of the family Felidae), making its survival dependent on access to cats. Most healthy adults are unaffected or only mildly sickened by a T. gondii infection, but it produces a variety of serious ailments, including toxoplasmosis, in those with compromised immune systems and in young children with immature immune defenses.
Torrey and his frequent research partner Robert Yolken of Johns Hopkins University have investigated the roles of influenza, T. gondii, and other pathogens in mental disorders. They undertook this research nearly a half century ago, when Freudian and psychosocial paradigms defined mental illness. As the next chapter explains, their efforts helped to shift this paradigm.
A microbial revolution
In his landmark book The Structure of Scientific Revolutions, Thomas Kuhn explains that those in the humanities—people who study, for example, eighteenth-century English literature, African American history, or German existentialism—are free to select the most convincing perspectives, assumptions, and causal frameworks within which to interpret their facts, but scientists are bound by a shared overarching theory. Kuhn defines that worldview, or Weltanschauung, as "what members of a scientific community, and they alone, share."
A paradigm shift is a revolution, for it seeks to overturn the prevailing worldview. But such an overturning is not to be undertaken lightly, because the scientific community's work, careers, and economies rest on the existing paradigm, and to nullify it is to cross the Rubicon, forever abandoning the rules that had previously defined scientific thought. Having embraced the theory of evolution, scientists cannot return to creationist myths to explain the variety of animal life. Having embraced germ theory, scientists cannot revert to believing that sin, demons, or wandering wombs cause madness or that malarious airs increase one's risk of contracting malaria. We are stuck, as it were, with what we know.
So we must choose our revolutions carefully. Yet the one this book describes—the recognition of infection as an important cause of mental illness—may have already begun; most of us just haven't realized it yet.
I say this because revolution takes place when anomalies arise that the existing worldview cannot explain. For example, it is hard to think of schizophrenia as a genetic disease when genetically identical twins are discordant—that is, when only one of the duo becomes schizophrenic. Such an anomaly doesn't immediately trigger researchers to discard the theory; in fact, many such anomalies are tolerated (or ignored) until a sort of critical mass accumulates that throws the field into "a state of crisis," according to Kuhn. New theories are then proposed, although sometimes they are not really new but ideas that have periodically resurfaced, been marginalized, decried as heresy, and forgotten. The hypothesis that infection causes or encourages common mental illnesses—and some uncommon ones—is an example, because as potential paradigm shifts go, it is a perennial. As I noted above, the theory has been with us since ancient times and reappears intermittently as part of the Western medical paradigm.
No one is suggesting that infection should completely replace stress, genetics, and psychological trauma as an explanation for mental illness, just that infection complements them and joins them as an important causative factor. And it is sometimes the primary factor.
The idea that a case of the flu might consign one to madness sounds fanciful. But consider that we are just now discerning the infectious roots of old familiar physical illnesses, many of which had been supposed to have psychological or behavioral triggers.
Cervical cancer, for example, was long ascribed to sexual immoderation in women and poor hygiene in their male partners, but it is now known to be the legacy of infection by strains of the human papillomavirus, HPV. Ninety percent of ulcers, which were once blamed on a spicy diet and uncontrolled stress, are now known to be caused by Helicobacter pylori. Contrary to the theory that held sway as late as the 1990s, heart disease is not a product of having a tense, hostile, angry type A personality but, often, of infection by bacteria including Streptococcus tigurinus and Chlamydophila pneumoniae.
Bacteria, viruses, parasites, fungi, and the infectious proteins called prions are surfacing as possible causes of mental illness as well, a theory that explains many previously mysterious anomalies. Schizophrenia, for example, has been traced to waves of influenza epidemics as well as to infections with bornavirus; species of adolescent anorexia and Tourette's syndrome have been connected to streptococcal infections that affect the basal ganglia; and autism is linked to marauding infections from children's own guts. This book explores the evidence for all of these and more.
In the seventeenth century, René Descartes posited the existence of two fundamental kinds of substance: mental and material.8 According to this Cartesian dualism, the mental has no spatial existence, and the material cannot think. Substance dualism became popular among scientists and clerics alike, perhaps because it does not preclude the religious belief that immortal souls occupy an independent realm of existence distinct from that of the physical world.9
But dualism is far more than a philosophy in medicine; it has long been a political stance as well, adopted as the default position that legitimized and laid a scientific veneer over the struggle of physicians to dominate medical care. Based in part on this theory of dualism, physicians were able to gradually appropriate the care of the physically ill from the clergy, who had established the religious hospitals that had originally assumed the care of the sick.
Still, although the law often required at least one resident physician in a psychiatric hospital or asylum, during the centuries before the discovery of effective medication, doctors were content to leave the care of the mentally ill to the clergy and nuns. However, the majority of the mentally ill were not confined to institutions. Michel Foucault has observed that madmen were allowed to roam freely in medieval Europe and temporarily confined only when their behavior became extreme enough to pose a threat. Moreover, such confinement was long the prerogative of the family, not the doctor. "From the seventeenth century to the nineteenth century, the right to demand the confinement of a madman belonged to the family: it was the family, first of all, that excluded madmen."10
- "Terrifying and comforting in equal measure. Infectious Madness will inspire healthy debate and...bold new strategies for prevention and treatment."—Priscilla Gilman, More Magazine
"A fascinating exploration of how common infections can affect mental illness."
—Shanda Deziel, Chatelaine
"Animpressive array of technical research is presented in a readable style in Infectious Madness."
"It used to be obvious what caused mental illness--depravity, a rotten soul, being in cahoots with the Devil. Or maybe just terrible mothering. We've escaped this primordial muck of attribution, learning that mental illnesses are biological disorders, complete with chemical and structural abnormalities in the brain, and with risk factors ranging from genes, hormones and fetal life to socioeconomic status. This superb book reviews the novel realization that infectious pathogens, and the immune system's response to them, can be risk factors for mental illness as well. The book has a broad, exciting range, considering 'contagion' in both the reductive sense, as well as an in the expansive societal manner. This is fascinating material and Harriet Washington is a great writer -- clear and accessible, witty, probing, and able to dissect the controversies in this field with great objectivity."
—Robert Sapolsky, author of Why Zebras Don't Get Ulcers
- "Your views on the causes of mental illness will be forever altered when you read this profoundly humane and transformative book." —Carl Hart, PhD, Associate Professor of Psychology, Columbia University
"Infectious Madness is a fascinating book about the role of infectious diseases in mental illness. Washington challenges us to expand our view of the causes, prevention, and treatment of emotional disorders. I highly recommend it!"
—Alvin F. Poussaint, MD, Professor of Psychiatry, Harvard Medical School
"With Infectious Madness, Harriet Washington sounds a much-needed alarm -- although not a welcome one. Turning old-fashioned germ theory inside out, she explains that we humans are the slow-moving interlopers in a world of microbes. And it's not just our health but our instincts, desires, feelings, and even our grasp on reality that are at stake."
—--Philip Alcabes, Professor of Public Health, Adelphi University, author of Dread: How Fear and Fantasy Have Fueled Epidemics from the Black Death to Avian Flu
- "In Infectious Madness, Harriet Washington confirms her position as one of our most thought-provoking medical writers. Led by Washington on a whirlwind tour of early modern medicine in the 18th century, germ theory, Western anorexia, African sleeping sickness, schizophrenia, and everywhere else, we will forever be unable to think of our microbial environment in the same way. The same, for that matter, might be said of our view of the social environment in which the collective enterprise of medicine transpires."—Samuel Roberts, PhD, Director, Columbia University Institute for Research in African-American Studies, and Associate Professor of Sociomedical Sciences, Columbia University Mailman School of Public Health
- On Sale
- Oct 6, 2015
- Page Count
- 304 pages
- Little Brown Spark