Books

Would Charles Darwin Have Taken Xanax?

Charles Darwin/Portrait by Julia Margaret Cameron

Editor's Note:

In her new book, Andy Warhol Was a Hoarder: Inside the Minds of History’s Great Personalities, health and science journalist Claudia Kalb gives readers a glimpse into the lives of high-profile historic figures through the lens of modern psychology, weaving groundbreaking research into biographical narratives that are deeply embedded in our culture. She covers Andy Warhol, Albert Einstein, Marilyn Monroe, Frank Lloyd Wright, and so many others. Here, she gives insight into Charles Darwin’s anxiety.

June 1858 was an especially trying month for Charles Darwin, both personally and professionally. The great scientist, then forty-nine years old and a devoted father, had suffered through the agonizing illness and death of his beloved ten-year-old daughter, Annie, in 1851, most likely from tuberculosis. Another child, Mary, had died in infancy, and now both fourteen-year old Henrietta and baby Charles, the youngest child of Darwin and his wife, Emma, were sick with infectious illnesses. “Etty” ultimately recovered, but Charlie, then about eighteen months old, succumbed to scarlet fever. “Our poor Baby died on twenty-eighth at night,” Darwin wrote in a letter to his cousin William Fox. “What a miserable fortnight we have had.”

Trouble often comes in cascading torrents, and this was certainly true for Darwin. During that same month of June, Darwin received an envelope by mail that would not only catapult his professional life into a state of unexpected turmoil but change the course of scientific history. The correspondence came from

Ternate, an island in the Dutch East Indies some 8,000 miles away from Downe, the small village southeast of London where Darwin and his family lived. Darwin knew and admired the writer, a fellow scientist and world traveler named Alfred Russel Wallace; his keen observations about native wildlife in a remote archipelago might have been welcome reading under other circumstances. But this correspondence contained far more than notes from a naturalist. Instead, in a concise essay, Wallace laid out an argument for evolution that was shockingly similar to the theory Darwin had been crafting – but not yet published – for almost two decades.

Wallace’s paper hit Darwin with volcanic force. There was no mistaking the similarities in the two men’s ideas about natural selection or the reality that Darwin, who had worked tirelessly to perfect his arguments, might be beaten to the punch on his life’s work. “I never saw a more striking coincidence,” Darwin wrote in a letter to his mentor, the esteemed scientist Charles Lyell, after reviewing Wallace’s work. An exceptionally ethical man, Darwin felt compelled to act honorably and informed Lyell that he would forward Wallace’s paper to a journal for publication, knowing full well what that would mean for his own painstaking research. “So all my originality,” he wrote to Lyell, “whatever it may amount to, will be smashed.”

These colliding events at home and at work would have been stressful for any human being. But the impact on Darwin was especially complicated, because he was a man of chronically bad health. For years, the scientist struggled with a long list of afflictions, including heart palpitations, stomachaches, and headaches, and throughout the course of his life his trials and his achievements were often paired with pain, immobilization, and isolation.

We know this from his letters, his autobiography, his methodical health journal, and the observations of family and friends. “If the character of my father’s working life is to be understood, the conditions of ill health under which he worked must be constantly borne in mind,” the botanist Francis Darwin reflected after his father died. “For nearly forty years he never knew one day of the health of ordinary men, and thus his life was one long struggle against the weariness and strain of sickness.”

And yet doctors could find nothing intrinsically wrong with him. So what made Darwin so sick? Since his death in 1882, biographers, historians, physicians, and mental health experts have weighed in with dozens of hypotheses, most of which fall distinctly into one of two categories: an organic or “physical” disease, or a disorder of the mind. Is it possible that Charles Darwin was battling an infectious tropical bug, picked up on his famous travels aboard the Beagle? Was it irritable bowel syndrome or cyclical vomiting syndrome? Or were Darwin’s lifelong symptoms psychosomatic – physical manifestations of ongoing mental stress?

The list of proposed diagnoses is so divergent you may as well be comparing a monarch butterfly to a great ape. But one key aspect stands out: Darwin was a worrier. He fretted about his children, about his work, about his deadlines, about his reputation, and, almost always, about what ailed him. Darwin, it could be argued, suffered from anxiety, one of the most common conditions on the planet. The revered scientist, the man who boldly proposed that “man is descended from a hairy quadruped furnished with a tail and pointed ears,” was altogether very human. Sometimes, like the rest of us, he was one big bundle of nerves.

Charles Robert Darwin was a perspicacious naturalist from his earliest days on earth. Born in Shrewsbury, England, on February 12, 1809, he was the fifth of six children of Robert Waring Darwin and Susannah Wedgwood. Robert, a monumental man of six foot two and more than 300 pounds, was a prominent and well-respected physician, as well as a successful financier; Susannah was the daughter of Josiah Wedgwood, an ambitious businessman who founded the Wedgwood pottery company and sold his elegant dinnerware to the highest ranks of British society, including the queen. His family’s wealth afforded Darwin a privileged upbringing, giving him abundant freedom to travel and pursue his passion for science. Financial security meant he could dedicate his life to deep thinking and analysis, ultimately challenging centuries-old assumptions about how plants, animals, and humans came to be.

Smitten with the outdoors, young Charles was fond of taking long strolls on the grounds of The Mount, the Darwins’ redbrick estate in Shrewsbury. Once, he became so lost in thought while walking to school that he fell off a high-set footpath, tumbling seven or eight feet to the ground. “Bobby,” as he was called early on by his family, also enjoyed fishing on the riverbank and wandering in his father’s vast garden, where he helped record details about the flowering of plants. Above all, young Charles loved collecting. His stockpile included household items, like coins and letter-sealing wax, but he was especially keen on the earth’s natural wonders: shells, birds’ eggs, plants, minerals, rocks, and insects. In an autobiography written during the latter years of his life, Darwin reflected on his enthusiasm for nature and how it distinguished him from his four sisters and his beloved older brother, Erasmus, who became a lifelong companion. “The passion for collecting, which leads a man to be a systematic naturalist, a virtuoso or a miser, was very strong in me,” Darwin wrote, “and was clearly innate, as none of my sisters or brothers ever had this taste.”

Darwin’s father has been described as an overbearing man in both personality and size (legend has it that he ordered his footman to test the floorboards in a new patient’s home to be sure they were strong enough to sustain his girth). In his autobiography, Darwin described his father in glowing terms: His kindness was “unbounded,” he was “generally in high spirits,” and “he was widely and deeply loved.” But his reminiscences were also peppered with references to a demanding side of Dr. Darwin, a man who was easily upset. “Many persons,” Darwin wrote, “were much afraid of him.” Darwin’s mother, by contrast, remained little more than a fleeting memory. Prone to intestinal upset and headaches, Susannah Darwin began experiencing severe stomach pains in July 1817, when Charles was just eight years old. She died just a few days later, possibly from an abdominal infection.

Studies have shown that the loss of a parent in early childhood can significantly increase the risk of both depression and anxiety later in life. Little is known about the full impact of his mother’s death, because Darwin had so little to say about her in his later writings. “I can remember hardly anything about her except her death-bed, her black velvet gown, and her curiously constructed work-table,” Darwin wrote in his autobiography. In a journal he noted that “except one or two walks with her I have no distinct remembrance of any conversations, and those only of very trivial nature.” Indeed, Darwin’s earliest memory had nothing to do with his mother at all. Instead, he remembered sitting on his sister’s knee as she cut an orange for him and then being startled when a cow ran by the window. Still, although he never expressed great feelings of loss from his mother’s death, he was profoundly affected by the way she died – quickly and inexplicably from pain in her stomach – according to Janet Browne, author of a highly acclaimed two-volume biography of Darwin. Darwin worried incessantly that he or his children had inherited a weak constitution from his mother’s side of the family, and he knew from her experience that sickness could quickly turn deadly. “With all the increased sensibilities of an adult, and then the passionate absorption of a husband and father,” Browne writes, “he came to dread the minutest sign of internal disorder for the destruction it might herald.”

Robert Darwin never remarried. In the wake of their mother’s death, Charles’s older sisters stepped in to help raise him, and, soon after, Dr. Darwin sent his young son to a local boarding school in town. Charles was not intellectually stimulated there – he later described the school as a lackluster place that taught learning by rote – nor was he a standout student. He often escaped and ran home to spend time with his family. Darwin later depicted himself as a “very simple little fellow,” who was considered by his teachers and his father to be “a very ordinary boy, rather below the common standard in intellect” – a modest appraisal that hardly matched the scientific genius he would become. Darwin found ways to enlighten himself, spending hours huddled under a window reading Shakespeare. But his chief passion early on was shooting birds. “I do not believe that anyone could have shown more zeal” for the sport, Darwin later reflected. “I became a very good shot.” At some point during his education, Darwin remembered in his autobiography, his father took note and warned Charles that his hobbies did not bode well for his future: “You care for nothing but shooting, dogs and rat-catching, and you will be a disgrace to yourself and all your family.”

To set him on a straight course, Dr. Darwin sent sixteen-year-old Charles to Edinburgh in 1825 to join his older brother, Erasmus, at medical school. It was something of a family tradition; both Dr. Darwin and his own father had studied to become physicians. The Darwin brothers enjoyed each other’s company, attending lectures together and wandering to nearby fishing villages. But Charles couldn’t bear the smells and spectacle of dissection or the eerie quality of the cadavers, some of which had been robbed out of graves and sold illegally to the school for profit. He was haunted, too, by the pain inflicted on patients during surgery (general anesthesia had yet to be discovered) and by the sight of blood, a phobia he claimed to have shared with his father. Although he dutifully showed up to observe two operations, he fled in horror before either one was completed and never went back. “To the end of his life he feared the sight of [blood], becoming almost hysterical if one of his own children accidentally grazed his or her skin, and quite unable to locate or apply a ‘plaister’ in his panic,” according to Janet Browne. “Though the children laughed at him, it was a very real revulsion.” Darwin, who lasted only two sessions at Edinburgh, never completed his medical studies.

With medicine no longer an option, Dr. Darwin proposed an alternative career for his son: clergyman. The path would start with an undergraduate university degree at Cambridge, followed by the steps required to receive ordination from the Church of England. It should come as no surprise that Darwin found his course of study at Cambridge less than inspired; he hated algebra, “did nothing” in the classics except attend a few required classes, and summed up his time there as “sadly wasted.” Two experiences, however, had a lasting impact. First, Darwin became infatuated with collecting beetles, which helped lay the groundwork for his later work as a naturalist. (He was so enthusiastic that one day he popped a beetle into his mouth so that he wouldn’t lose it; the insect, less thrilled about this arrangement than Darwin, expelled a noxious fluid, burning the scientist’s tongue.) The second critical development was Darwin’s friendship with John Stevens Henslow, a brilliant young professor of botany. The two became intellectual confidants, taking long walks together and discussing scientific developments of the day. Their friendship, Darwin later reflected, was “a circumstance which influenced my whole career more than any other.”

It was Henslow, after all, who sent Darwin a letter in August 1831 asking him if he’d like to embark on a scientific journey on a ship called the Beagle. The vessel’s captain, Robert FitzRoy, had been commissioned by the British Admiralty to take the Beagle on a second voyage (the first had taken place between 1825 and 1830) to continue a survey of the South American waterways. FitzRoy, who was aboard the first time, was looking for a scientific associate to keep him company and to engage in exploration. At first, Darwin’s father, who would have to finance his son’s expenses, vehemently objected. Worried, among other things, that Charles would never commit to a profession, he called the plan a “useless undertaking” and a “wild scheme.” But Darwin had an ally in his uncle, Josiah Wedgwood, and he successfully sought Uncle Jos’s help in changing his father’s mind. “The undertaking would be useless as regards his profession,” Wedgwood wrote to Darwin’s father, “but looking upon him as a man of enlarged curiosity, it affords him such an opportunity of seeing men and things as happens to few.”

On December 27, 1831, twenty-two-year-old Charles Darwin set sail on a journey that would alter the trajectory of his life and transform the history of science. The trip would also serve as a signpost for Darwin’s health. Just before departing, Darwin exhibited signs of intense anxiety, and several months after returning, he began suffering from the symptoms that would debilitate him for decades, including what may have been panic attacks.

There is overwhelming evidence that Darwin was sick, often severely so, for much of the latter half of his life. He referred to his ill health repeatedly in his correspondence and painstakingly recorded his symptoms in a health diary whose entries included specific complaints (“boil under arm,” “slight fit of flatulence”) as well as overall ratings (“goodish” and “poorish” to “well very” and “well barely.”) Darwin’s extensive list of woes featured fatigue, dizziness, eczema, boils, muscle weakness, cold fingers and toes, black spots, and even hysterical crying. But his overwhelming complaint was abdominal distress, with ongoing bouts of nausea, vomiting, and flatulence. Over the years, Darwin’s symptoms have spurred researchers to propose an alphabet soup of diagnoses: agoraphobia, anxiety, appendicitis, arsenic poisoning, barnacle preservative allergy, brucellosis (bacterial infection), Chagas’s disease (infection resulting from a tropical bug bite), Crohn’s disease, cyclical vomiting syndrome, depression, gastritis, gout, hepatitis, hypochondria, irritable bowel syndrome, lactose intolerance, malaria, Meniere’s disease (inner ear disorder), mitochondrial disease (genetic disorder inherited from maternal lineage), neurasthenia (nervous disorder), obsessive-compulsive disorder, panic disorder, paroxysmal tachycardia (rapid heartbeat), peptic ulcer, pigeon allergy, pyroluria (blood disorder), and social anxiety. The only thing anyone can say with any certainty about Darwin and illness is that he died, at the age of seventy-three, of heart disease.

What makes Darwin’s case so intriguing is that it exemplifies the powerful interplay between body and mind – the reality that fatigue and vomiting can signify an intestinal infection in one case and emotional upheaval in another. Or both at the very same time. Even without a confirmed diagnosis, though, it is clear that Darwin struggled with a sensitive disposition. This became readily apparent as the scientist waited to board the Beagle. The ninety-foot vessel had been scheduled to set sail from England’s port town of Plymouth in October of 1831, but was delayed by bureaucratic impediments and heavy gales until the end of December. The intervening months were “the most miserable which I ever spent,” Darwin later wrote, as he struggled with ailments. His symptoms during this time included chest pains, palpitations, abdominal discomfort, and fear of dying, according to Dr. Ralph Colp Jr., a Columbia psychiatrist who spent decades poring over Darwin’s letters, journals, and manuscripts. Darwin felt “giddy

& uncomfortable” in the head and he was eager to escape the predeparture bustle of preparations. “I look forward even to sea sickness with something like satisfaction,” he wrote in a letter to Henslow as the ship prepared to depart, “anything must be better than this state of anxiety.”

People with anxiety often worry excessively about what might happen and anticipate the worst – “everyone’s going to laugh at my speech,” “my headache must be a brain tumor.” As much as Darwin was eager to take the journey, he was nervous about what he might encounter along the way, according to Colp: the close quarters on the ship, the coarse behavior of the crew, the possibility that he might become ill or even drown. He also felt uneasy about being away for such an extended period: “I was out of spirits at the thought of leaving all my family and friends for so long a time, and the weather seemed to me inexpressibly gloomy,” he later reflected. And he began to exhibit a fear about his symptoms – hypochondria is rooted in anxiety – as well as an obsession about his health that would reappear throughout his life. “I was also troubled with palpitations and pain about the heart,” Darwin wrote, “and like many a young ignorant man, especially one with a smattering of medical knowledge, was convinced that I had heart disease.”

The journey, which spanned 40,000 miles from England to South America, Australia, and Africa, had plenty of challenges, both practical and social. In letters home, Darwin documented the rough seas and navigational mishaps. He struggled with occasional bouts of fever, intestinal distress, a swollen knee, occasional boils and headaches, and, more than anything, severe seasickness. Darwin spent much of his time at sea nibbling on raisins (his father’s prescription), lying in his hammock, and retching. Although he and FitzRoy fared well together overall and engaged in deep and spirited discussions, Darwin remembered the captain (who would commit suicide years later) as exceedingly temperamental, suspicious, and morose. Darwin missed evening chats with his friends and fretted about what would become of his endeavors after the trip. “It is disheartening work to labour with zeal & not even know whether I am going the right road,” he wrote to his cousin in October 1833.

The young adventurer was mostly in good physical form, however, while exploring on land, which composed the bulk of the journey. He rode hundreds of miles on horseback, sometimes through hail and snow; he slept outside; he climbed into the Andean foothills; he hunted animals for Christmas dinner; he ate roasted armadillo; he survived an earthquake and a near-capsizing of the boat by a glacier; he even “saved his crewmates by rescuing a rowboat from a tidal wave” in Tierra del Fuego, according to his biographer Janet Browne. Along the way, Darwin collected some 10,000 specimens – plants, fossils, rocks, animals – and shipped them home for analysis. In the end, Darwin “proved the fittest and, in many respects, the toughest man on board,” the British physician Sir George Pickering noted in his book, Creative Malady. No mention was made of the illness that would later dominate his life, Pickering writes: “He was too active and too busy acquiring new experiences.”

The Beagle journey, scheduled to last two years, stretched to five. When Darwin returned to England in October 1836, he was a changed man. His father, upon seeing him for the first time after the voyage, turned to Darwin’s sisters and said, “Why, the shape of his head is quite altered” – a comment Darwin took as symbolic confirmation that his mind had developed through the course of his Beagle pursuits. No longer foraging for a career, Darwin was now a world-traveled naturalist who had assembled evidence – even if he didn’t realize it at the time – for his theory of evolution.

Darwin’s health would also undergo a dramatic metamorphosis. Stress of any kind is a common trigger for anxiety, and by the fall of 1837, when he was twenty-eight years old and living in London, Darwin had taken on a weighty workload. His many activities included serving on the governing council of London’s Geological Society, finishing a detailed account of the Beagle voyage, and scribbling out his earliest musings about evolution in a series of notebooks about the “transmutation of species.” He also began to struggle with poor health. “I have not been very well of late with an uncomfortable palpitation of the heart,” he wrote in a letter to Henslow that year, “and my doctors urge me strongly to knock off all work and go and live in the country, for a few weeks.”

Worriers fear the unknown and tend to have difficulty making decisions. Around this time, Darwin was also wrestling with a major question in his personal life: whether or not to marry. A thoughtful and exacting man, he scribbled out the pros and cons under “Marry” and “Not Marry” columns on scraps of paper. The upsides, Darwin noted, included companionship and “the charms of music and female chit-chat.” The advantages to remaining single: no forced visits to relatives, relief from the “anxiety and responsibility” of children, and freedom to do as he liked. “Eheu!! I never should know French – or see the Continent – or go to America, or go up in a Balloon,” he lamented about marriage, while at the same time bucking himself up to move forward. “Never mind my boy – Cheer up – One cannot live this solitary life, with groggy old age, friendless and cold and childless staring one in one’s face, already beginning to wrinkle.” By the time Darwin finally decided to propose to his cousin Emma Wedgwood, he was taxed by his reservations, not to mention the pressure of his work. His proposal was less than a boisterous occasion. “Darwin was exhausted by the nervous strain,” wrote Janet Browne, “with a bad headache.”

The couple would go on to enjoy a solid and loving forty-three-year marriage, and Emma became Darwin’s dedicated caregiver throughout his many bouts of ill health. But his wife could not heal Darwin – far from it. During their early years of marriage, the scientist recorded a slew of debilitating symptoms, including chills, trembling, weakness, severe flatulence, vomiting, and headaches. His poor health fluctuated with his work and with Emma’s first two pregnancies. Darwin’s aversion to pain and bleeding may have made him especially sensitive to the discomfort his wife was going through, according to Colp. The period before delivery, Darwin wrote in a letter to his cousin William Fox, “knocked me up, almost as much as it did Emma herself.” Darwin also worried excessively about the well-being of his children, fearing not only that they had inherited a weak constitution but that they might be affected by the effects of inbreeding, which increases the risk of birth defects and illness. “My dread is hereditary ill-health,” Darwin wrote to Fox in 1852, when his ninth child was almost a year old. “Even death is better for them.”

Ultimately, it was Darwin’s work – primarily his writing of On the Origin of Species – that occupied most of his time and his worry. In 1844, Darwin completed a 189-page draft of his theory, with instructions for Emma to publish it if he died. But fourteen years later, when Alfred Russel Wallace’s correspondence arrived at his doorstep, Darwin still had not finalized his work. The cause for “Darwin’s delay,” as it has been dubbed, has been scrutinized and debated for years. He was of course busy with his marriage, his children (seven out of ten would survive into adulthood), and other major writing projects, including a five-volume collection documenting the plant and animal specimens he had collected during the Beagle voyage, and four reports on the diversity of barnacles. He also needed time to analyze everything, from the breeding habits of pigeons to the variation among strawberries and pears. And he wanted to be right. Well aware of half-baked speculations about evolution that had already been published, including an account by his grandfather Erasmus, Darwin’s account needed to be as tight as an Anchor Bend knot.

There is little doubt that Darwin struggled with feelings of anxiety about publishing his theory, especially early on. Known to be a modest and affable man who hated both controversy and the public spotlight, he knew that his proposition that the earth’s creatures were not uniquely designed by a higher power, but had instead evolved and adapted over time, would outrage the most pious members of society, upending centuries of religious belief about divine creation. Darwin had lost much of his own religious faith after the death of his daughter, Annie, in 1851, but his wife was a devout Christian; publishing could upset not only the greater masses but his most loyal supporter at home. His theory, he wrote to a friend, amounted to “confessing a murder.”

It was competition that would finally push Darwin to publish his work. Charles Lyell, who had received Darwin’s letter with Alfred Russel Wallace’s correspondence, presented both scientists’ theories jointly at a scientific meeting in July 1858 – one month after Wallace’s initial communication had arrived. It was a respectable solution that received surprisingly little notice and gave Darwin time to move forward honorably. Over the next year, he worked tirelessly to finalize his 500-page account. He also felt sick. As far back as 1838, Darwin had drawn a connection between his brain and his gut, writing that “I find the noddle & the stomach are antagonistic powers, and that it is a great deal more easy to think too much in a day, than to think too little.” Now, as he raced to the finish line in 1859, Darwin again attributed his physical distress to the strain of completing his “abstract,” as he called it, and he longed for it all to be over. “I have been extra bad of late, with the old severe vomiting rather often & much distressing swimming of the head,” he wrote to Fox. “My abstract is the cause, I believe of the main part of the ills to which my flesh is heir to.”

There is a critical difference between fear and anxiety. Fear is like a guest who shows up without warning and leaves quickly; anxiety unpacks its suitcase, settles into your brain, and overstays its welcome. The difference comes down to real and imagined threats. Fear is a necessary part of our evolutionary makeup – a hardwired reaction to danger that compels us to run from a stampede of elephants or a tsunami and gives us the energy to do so. Our stress hormones spike, our hearts pump faster, our blood pressure increases. Anxiety, which causes some of the same physiological symptoms, is all about perceived hazards, not ones that are actually staring us in the face.

Scientists have pinpointed the circuitry for fear in a cluster of neurons called the amygdala, located deep inside the brain. Studies have revealed that a damaged or missing amygdala changes the way an animal responds to peril. Rats with an impaired amygdala will hang out with a sedated cat – an animal they’d normally flee from – and even nibble its ear. Healthy monkeys placed in close proximity to a snake, real or fake, will withdraw, avoid eye contact, and take their time reaching for tempting food situated near the reptile, be it M&M’s, Froot Loops, or cocktail peanuts (we are related!). Monkeys whose amygdalas have been surgically removed, by contrast, act uninhibited; they go after the treats quickly, despite the possible risk, and even show curiosity about an animal they would otherwise evade.

Human studies are equally intriguing. Several years ago, researchers tried to evoke fear in a patient whose amygdala was destroyed by a rare congenital disorder. They took the patient, known as SM, to a spooky Halloween tour at the Waverly Hills Sanatorium, formerly a tuberculosis infirmary in Louisville, Kentucky, which was said to be haunted by dead patients and medical staff. As other adult members of the group screamed with fright, SM smiled and laughed at the monsters that jumped out to scare her. She even startled one of them by poking him in the head. Later, she reported feeling great excitement – as if she were riding a roller coaster – but zero fear.

The scientists showed SM movie clips from horror films, including “The Shining” and “The Silence of the Lambs”; she found them entertaining, not terrifying. And even though she said she hated snakes and spiders, SM showed no apprehension when taken to an exotic pet store, where she displayed an unusual compulsion to touch the animals, reporting that it was “so cool” to hold a slithering snake and feel its darting tongue. Her curiosity was so great, says Justin Feinstein, the study’s lead author and a clinical neuropsychologist at the Laureate Institute for Brain Research in Tulsa, Oklahoma, that a store employee had to stop her from touching a tarantula so that she didn’t get bitten.

It is well established that the amygdala acts as a warning system for external threats. Scanning the horizon like a searchlight, it sends chemical signals to other parts of the brain when danger is spotted. But as scientists unravel the science of fear, they are discovering that the amygdala’s role is far more complex than originally imagined. It isn’t, it turns out, the be-all and end-all of fear. This became clear recently when Feinstein and his colleagues put SM up to a different kind of challenge. Given her prior reactions, the scientists expected SM to respond without apprehension when they put a mask over her nose and asked her to inhale oxygen laced with carbon dioxide, a standard laboratory fear test. To the researchers’ surprise, SM gasped for air, ripped off her mask, and had a full-blown panic attack. Her reaction turned out to be far more intense than most of the control subjects with fully functioning amygdalas; they had trouble breathing, but less than a quarter of them reacted with panic.

Feinstein’s interpretation of these findings is that when a threat emerges inside the body – you breathe in bad air or feel pain in your heart – the primitive brain stem, not the amygdala, takes over. Not only that, when the amygdala is working as it should be, it may actually serve to damp down anxiety rather than ramp it up. This seems to be corroborated in other studies, which have found that people who suffer from panic attacks have a significant amount of atrophy in their amygdalas. If a damaged amygdala fails to inhibit panic, Feinstein explains, the brain might overreact to things that aren’t really that dangerous – a bridge or a crowd of people – and trigger a series of panic attacks that ultimately leads to a condition known as agoraphobia, an avoidance of places and circumstances where panic might occur.

Just as allergies manifest in different ways – hives, rashes, watery eyes, sneezing – anxiety disorders can appear in multiple guises, often in the same individual. The DSM lists eleven types of anxiety disorders, including panic disorder and agoraphobia as well as selective mutism (anxiety so severe a child cannot speak in school or other social settings) and the more common generalized anxiety disorder (pervasive and chronic worry about a variety of everyday issues). Today, Darwin’s aversion to blood would likely fall into the category of a specific phobia; other common phobias include a fear of spiders, heights, and flying. Darwin was also apprehensive about public speaking, a classic feature of what is now classified as social anxiety disorder and characterized by extreme worry about being scrutinized and humiliated. In a letter to his son, Willy, Darwin wrote that when he was required to read papers as secretary of the Geological Society, “I was so nervous at first, I somehow could see nothing all around me, but the paper, & I felt as if my body was gone, and only my head left.” At another time, he noted that speaking for just a few minutes at a scientific society meeting “brought on 24 hours [of] vomiting.”

In a report published in the Journal of the American Medical Association in 1997, two medical doctors concluded that Darwin suffered from panic disorder, an anxiety disorder marked by recurrent panic attacks. These attacks are characterized by a sudden onset of fear accompanied by severe physical symptoms that can erupt unexpectedly. Darwin experienced a range of features associated with panic disorder, the researchers wrote, including palpitations, shortness of breath (which he described as “air fatigues”), crying, insomnia, abdominal distress, and feelings of imminent death. In the midst of a panic attack, it is not uncommon for people to worry that they are having a heart attack and are likely to die. The doctors also described Darwin’s own accounts from his health journals – waking during the night feeling fearful and experiencing “swimming of the head,” trembling hands, and “attacks of sickness” – as experiences consistent with the condition. Darwin’s illness “followed a waxing and waning course typical of the disorder,” the authors wrote. “His attacks caused him great distress and interfered with his work and social life.”

The doctors theorized that Darwin also suffered from agoraphobia, a Greek and Latin term that translates as “fear of open spaces.” The two conditions are often linked (until recently they fell under one diagnosis in the DSM), because people who have repeated panic attacks tend to avoid the places and situations that made them fearful in the first place – a bridge, a crowded theater, an elevator, or being alone. In Darwin’s case, he actively shied away from public appearances, scientific meetings, and social interaction, because participating in these activities had a deleterious effect on his health. Soon after their marriage in 1839, Charles and Emma moved from London to Downe, where Darwin put stringent limitations on the time he spent out of his home. “During the first part of our residence we went a little into society, and received a few friends here; but my health almost always suffered from the excitement, violent shivering and vomiting attacks being thus brought on,” he later reflected in his autobiography. Darwin did communicate actively with family, friends, and scientists by exchanging some 15,000 letters, but his preference was to stay physically close to home with his wife by his side. “I dread going anywhere, on account of my stomach so easily failing under any excitement,” he wrote to his cousin in 1852. His life was comfortable, he told Fox, but “it is the life of a hermit.” Even a major conference held to debate On the Origin of Species was too much for him. He wrote a note saying he couldn’t attend because of stomach pain.

A series of landmark studies suggest that key features of anxiety, which runs in families, are detectable in the earliest days of life. In 1989, Harvard psychologist Jerome Kagan launched a longterm study in which he observed how a group of four-monthold babies responded to unfamiliar people and toys. Some of the babies remained calm and relatively unfazed, but about twenty percent had strong reactions – they cried, they pumped their arms and legs, they arched their backs. Kagan and his colleagues followed those babies for two decades and discovered that the highly reactive infants were more likely to be shy, cautious, and anxious children and adults.

Baby Darwin might have made an interesting research subject. In his youth, he exhibited physical symptoms – trembling, chills, shivering, and intestinal upset – in response to both pleasant and unpleasant events, according to Colp, the Columbia psychiatrist. He left a dog show early after seeing one of the animals react to its owner’s reprimand, telling a friend, “I can’t stand this any longer; how those poor dogs must have been licked.” After shooting his first bird, Darwin later recalled, his hands were trembling so much with excitement that he could barely reload his gun. Listening to music prompted such intense enjoyment “so that my backbone would sometimes shiver,” he writes in his autobiography. Like the highly reactive babies in the Harvard study, Darwin responded to stimuli in a very physical way and may have been primed for anxiety from an early age.

He would have been in excellent company today. Anxiety disorders are the most ubiquitous of mental health conditions, affecting some forty million Americans. We live at a time when it’s easy to become nerve-racked by the minute choices that freedom affords us (not just should I buy organic milk, but what brand should I buy?), by the economy, by terrorism, by the mobile devices that interfere with our sleep. Inner peace is clearly hard to come by, as confirmed by how many people are desperately trying to find it. Guess what ranks as the top psychiatric medication prescribed in the country? The anti-anxiety drug alprazolam, which goes by the brand name Xanax. In 2012 alone, 49 million prescriptions were written.

We may think, in the twenty-first century, that we are more nervous than ever – that our “age of anxiety,” as W. H. Auden dubbed it in his 1947 Pulitzer-winning poem, is the most skittish of all. The reality, of course, is that human beings have been worriers for millennia. As Scott Stossel, editor of Atlantic magazine and author of the book My Age of Anxiety, puts it: “As soon as the human brain became capable of apprehending the future, it became capable of being apprehensive about the future.” Indeed, by the time Darwin died, anxiety had become a kind of cultural affliction. At the turn of the 20th century, the diagnosis du jour among accomplished and upper-crust Americans was “neurasthenia” or “nerve weakness.” Symptoms, which included depression, insomnia, migraines, fatigue, anxiety, and even premature baldness, were deemed to be caused by the stresses of the industrial revolution and an overtaxed brain.

A host of well-known figures were said to suffer from neurasthenia, including the James siblings (Henry and Alice, both writers, and William, the influential philosopher) as well as President Theodore Roosevelt. Often, they were treated with “rest cures” and sent off to bed. In 1901, a Columbia University psychiatrist proposed that Darwin himself had neurasthenia – and a chronic and severe case of it, the doctor wrote, caused by the scientist’s difficult journey on the Beagle and a “life of hard intellectual work.” If only Darwin had given up all work for a year or two after his return and “had lived a life of rest and diversion, free from the daily toil of writing books, correcting proofs, and correspondence,” the doctor lamented, “I believe a cure would have been brought about and his subsequent life more filled with joy and alleviation than it was.”

If only it were that simple. Throughout the course of his illness, Darwin consulted numerous doctors – even Queen Victoria’s own physician – and submitted himself to a wide array of treatments, including ice packs placed on his spine, mercury pills, antacids, bismuth (the active ingredient in Pepto-Bismol), lemons, codeine, and electrical stimulation of his abdomen. His favorite therapy, at least initially, was the Victorian “water cure,” which required spending several months at a spa, where Darwin sweated next to hot lamps, had his body rubbed with cold towels, soaked his feet in cold baths, and had wet compresses pressed on his stomach. The treatment also required getting up early, eating moderately, avoiding sugar, drinking water, and walking. Back home, he kept up as best he could, taking frigid showers, even in the winter, and cutting back on his wife’s sweet puddings. Nothing worked for long.

Scott Stossel can relate. A “twitchy bundle of phobias, fears, and neuroses” from around the age of two, Stossel has struggled with severe anxiety all his life, including panic attacks and a slew of specific phobias – heights (acrophobia), fainting (asthenophobia), flying (aerophobia), vomiting (emetophobia), and even cheese (turophobia, because the smell reminds him of throwing up). Although he has sought and tried a host of treatments, including medication, hypnosis, and even whiskey, “nothing has been a panacea,” he says. Stossel finds comfort in Darwin’s story, knowing that he is “hardly alone in having both a mind and a belly so easily perturbed by anxiety.” Plenty of others are right there with him. Barbra Streisand was performing in Central Park in 1967 when she forgot the lyrics to the song she was singing, prompting a performance anxiety so intense that it kept her off the public stage (other than small clubs and charity events) for almost 30 years. Football player Ricky Williams, who was awarded a Heisman Trophy in 1998, suffered from such a bad case of social anxiety that he resorted to giving interviews with his helmet on.

Stossel believes, though, that some of the traits associated with his anxiety, including his conscientiousness and fear of screwing things up, may have helped make him the successful person he is today. A well-known scientific principle known as the Yerkes-Dodson law supports his theory in its assertion that if you’re not worked up at all, you won’t ace a test or hit a home run. Nor will you succeed if you’re so overly stressed that you become paralyzed with fear. The key to optimal performance: a moderate dose of anxiety that will keep you energized, focused, and motivated.

Darwin was, of course, very sick. Even if anxiety did help fuel his momentous achievements, his physical symptoms were often overwhelming. “I’m staggered that he was able to persist through his extreme debilitation,” says Stossel. Today, treatment for anxiety includes psychotherapy, medication, and lifestyle adjustments, including plenty of exercise and more sleep. The goal, says Dr. Craig Barr Taylor, director of the Anxiety Disorders Clinic at Stanford Medical Center in Palo Alto, California, is to calm down the worry to a level that allows an engaged and satisfying existence. “A lot of what we do in clinical treatment is not really to get rid of anxiety,” he says, “it’s to help you find a way to deal with it so you can lead a full life.”

It would be foolhardy to assert that Darwin’s problem was 100 percent anxiety, plain and simple. It’s entirely possible that he suffered from other illnesses as well, including Chagas’s disease, irritable bowel syndrome, or cyclical vomiting, any of which could have been exacerbated by stress. Still, anxiety seemed to infuse his very being, entwining itself with whatever else may have been coursing through his brain and his body.

In the end, On the Origin of Species did not set off quite as great an uproar as Darwin may have imagined, in part because he dedicated a chapter to “Difficulties on Theory,” which anticipated and addressed the concerns of critics. But there was plenty of public debate, which Darwin managed to avoid as an alliance of supporters stepped forward to defend his work. His health problems persisted after publication of his celebrated dissertation, but during the last decade of his life – as he turned his attention to far less contentious topics – his symptoms subsided, and he finally found relief. His last book, one of his most popular, was about earthworms.

In the early months of 1882, Darwin experienced chest pains. Emma, his constant protector, attended to him and kept him company. On April 19, he died at age seventy-three of what doctors called “angina pectoris syncope,” or heart disease, after reportedly telling Emma that he was not afraid to die. By the end of his life, this kind, modest and brilliant scientist had become an intellectual celebrity. He expected to be buried in the churchyard in his hometown, next to two of his children. But in one of history’s great ironies, the man who overturned religious doctrine with barnacles and pigeons and apes found his final resting place in a velvet-draped coffin at the illustrious Westminster Abbey.

For Darwin, nothing was ever simple.