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The Rabbit Effect

Live Longer, Happier, and Healthier with the Groundbreaking Science of Kindness


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About The Book

This groundbreaking and life-changing work based on the latest research effectively demonstrates “the profound impact that love, connection, and kindness have on our health” (Mark Williamson, PhD, director of Action for Happiness).

When Columbia University doctor Kelli Harding began her clinical practice, she never intended to explore the invisible factors behind our health. But then there were the rabbits. In 1978, a seemingly straightforward experiment designed to establish the relationship between high blood cholesterol and heart health in rabbits discovered that kindness—in the form of a particularly nurturing post-doc who pet and spoke to the lab rabbits as she fed them—made the difference between a heart attack and a healthy heart.

As Dr. Kelli Harding reveals in this eye-opening book, the rabbits were just the beginning of a much larger story. Groundbreaking new research shows that love, friendship, community, and our environment can have a greater impact on our health than anything that happens in the doctor’s office. For instance, chronic loneliness can be as unhealthy as smoking a pack of cigarettes a day; napping regularly can decrease one’s risk of heart disease; and people with purpose are less likely to get sick.

At once paradigm-shifting and empowering, The Rabbit Effect illuminates vital public health research showing kindness in our day-to-day lives can make the “world a healthier, happier place. I recommend this book highly for anyone who wants to live more healthfully” (Christy Turlington Burns, and CEO of Every Mother Counts).


The Rabbit Effect Introduction What Are We Missing in Medicine?
The path to helping people as a doctor seemed straightforward when I arrived at medical school at the University of Rochester. On the first day of my first year, I sat anonymously in the auditorium with ninety-nine other classmates. Clad in spotless white coats, we prepared to cloister ourselves inside the walls of the Strong Memorial Hospital complex. Everything we needed to know about the inner workings of the human body lay within—or so I thought.

For the next four years, my classmates and I followed the well-worn route to the knowledge of medicine: peering through microscopes, cramming for exams in silent library cubicles, and racing through a maze of fluorescent-lit corridors to see patients. During this time, I caught glimpses of daylight reflected off white linoleum. I rarely felt the sun on my skin, the wet grass of spring, or even the bustling city beyond the brick fortress of the hospital complex. Through these intense and completely immersive years, which extended through residency and fellowship, the world outside the hospital seemed irrelevant to my work as a physician. If it weren’t for the white rabbits, I might never have walked out the sliding doors of the medical center in search of a new perspective on health.

As a medical student on the hospital wards, I noticed odd patterns with patients, observations unmentioned in my medical books. Two patients with the same diagnosis would have two very different courses of illness; one would become gravely ill, while the other carried on an almost normal life. Others I saw had medically unexplained symptoms; I’d search and search, but there was nothing in my texts that supplied a reason for their reported ills. Initially, I felt a vague sense of discomfort with these inconsistencies. I didn’t have the narrative or framework to understand them, so I tried to ignore the puzzles they posed. But the nagging feeling that I was missing something in my diagnoses refused to go away. I had accounted for all the usual biomedical explanations. What were the hidden factors in these individuals’ health that I wasn’t seeing? I was determined to investigate further.

My first suspect was mental health. I wondered if the mysterious interaction of the mind and body could explain why some patients fared better than others. Since no residency-training program addresses the interaction between mental and physical health directly, I self-designed my course of study. First I immersed myself in internal (adult) medicine training at Mount Sinai Hospital in New York City, followed by psychiatry residency training at Columbia University’s Irving Medical Center. I remained at Columbia for a National Institute of Mental Health (NIMH) biological psychiatry research fellowship and focused on medically unexplained symptoms. I also became boarded in psychosomatic medicine (consultation-liaison psychiatry). I was a woman on a mission.

Trying to tease apart medical and psychiatric diagnoses is my area of specialty. Clinically, I made the emergency room my home, seeing patients with both acute medical and behavioral concerns. While this means I’ve seen more than my share of people found naked on New York City streets, it also has provided a front-row seat to both the power and the limits of traditional biomedical knowledge. Despite the fact that I’d trained in a specialty that gave me more insight into people’s minds, I still felt I was missing something. Connections between medical symptoms and mental states seemed clear, but why did some people fare so much worse than others when, medically, that shouldn’t have been the case? I wanted to understand the different underlying conditions that influence the course of a disease. And then one day, much like Alice, I followed a white rabbit.

“You might want to look at the rabbit studies,” Dr. Arthur Barsky suggested. With his carefully side-parted hair, round tortoiseshell glasses, and fatherly demeanor, Arthur was a combination of Clark Kent and a doctor from a black-and-white 1950s medical drama. A member of the Harvard Medical School faculty, and one of my mentors during my fellowship at Columbia, Arthur revealed his secret identity through his research—he, too, was fascinated by medical mysteries. And he dared to question whether answers to a patient’s health problems always lie within the traditional boundaries of medicine.

After my fellowship ended, Arthur and I reconnected at a scientific meeting at a symposium I moderated for Dr. Elizabeth Blackburn, the Nobel Prize–winning biologist who discovered the molecular nature of telomeres, the protective caps on our DNA involved in life span. After the meeting, Arthur and I started a series of conversations that began with telomeres and the aging process. Our conference calls, which stretched over years, became a critical part of my education, beyond what’s listed on my CV. We brainstormed about clinical curiosities: patients who defied expectations and did well despite terrible diagnoses; curious coincidences such as the increased odds of dying on one’s birthday, or in the six months after a spouse dies, or following a broken heart or a surprise party. We discussed patients who get better with inert medications (the placebo effect) and patients who develop severe side effects from pills with no active ingredients (the nocebo effect). How exactly did the mind affect the body? What else might contribute to physical symptoms?

Between our calls, I’d scour the medical literature for studies on the little-understood topics we discussed, such as the relationship between telomere length, premature aging, and life purpose, and then summarize findings for the next discussion. Arthur and I explored the limits of medical understanding, rooted in science and open to possibility. It was Arthur, through his suggestion of the white rabbits, who helped me escape my limited view of health from inside the hospital’s cocoon. By then, we’d both become increasingly obsessed with understanding the mystery: What are we missing in medicine that’s crucial to health?

In medicine, including psychiatry, when we ask what we are missing, we usually find the answer through a research trial or a new drug. The breakthroughs that result from this kind of biomedical research, especially in recent decades, have had substantial consequences for our health. High-tech modern medicine is indisputably superb at keeping someone alive when crisis strikes. Advances in trauma surgery save countless lives. Biomedical advances also transform death sentences into chronic diseases.

In fall 1995 a physician told a razor-thin thirty-seven-year-old man named Robert to get his affairs in order because he had less than a few months left to live. Over two years later, when I attended a fund-raiser in Washington, DC, I met Robert, looking dapper in a tux. Robert’s turnaround from AIDS was miraculous. He had put on weight and even developed a bit of a belly, a side effect of the medicine. He bought season tickets to the Kennedy Center with friends and was back to playing Chopin on the piano. The revolutionary class of medication for HIV called protease inhibitors had arrived on the market just in time to save him, and countless others. Many individuals like Robert have discovered life on the other side of a death sentence thanks to biomedical advances.

Yet, despite our scientific progress, Americans are remarkably unhealthy. In 2016 the United States ranked forty-third in the world for life expectancy. Unless we change course, the US is expected to drop to sixty-fourth place by 2040.1 In 2015 life expectancy for Americans declined for the first time in two decades, while it rose in other wealthy nations. And then the numbers dropped again in 2016 and 2017. During this period, Nobel Prize–winning economist Angus Deaton and his wife, fellow Princeton University professor Anne Case, reported a spike in mortality for middle-aged white men and women with less than a college education. Their data showed that between 1999 and 2013, half a million people died unexpectedly.2 That’s as if the entire population of St. Louis, Missouri, just disappeared.

It’s not just life expectancy. America has consistently poor performance on numerous global health measures. For instance, despite spending more than any other country for hospital-based maternity care the US is ranked forty-sixth in the world for maternal health.3 It also has the worst rate of maternal deaths in the developed world with a rising maternal mortality rate (from 17 deaths per 100,000 births in 2000 to 26.4 deaths per 100,000 in 2015).4 Compounding the heartache, American children are less likely to reach the age of five than children in other developed countries like Japan. Starting at birth, Americans fall far below other wealthy nations on many standardized health indicators, such as infant mortality, car crashes, mental illness, teen pregnancies, heart disease, imprisonment, homicides, substance use, obesity, and premature death.5

America has one of the worst gaps between the health outcomes of rich and poor people, which serves as a key marker of a nation’s well-being. Out of the thirty-two wealthiest countries in the world, the US ranked thirty-second on the wealth-health gap.6 The US is such an outlier of extreme income and health inequality, we are practically not even on the same graph.7 The same unfortunately holds true for childhood emotional well-being.8 Even the rich don’t live as well as they could. Our comparatively worse health cuts across lines of privilege and race. Wealthy, educated white Americans can expect to die several years younger than equally well-off individuals around the world.9

And despite, or perhaps because of, America’s status as a global leader in biomedicine, it is also by far the world’s most expensive place to get sick. Maybe you or a family member has put off a test or a follow-up visit to save money like one in five Americans.10 I know I have, even as a doctor working in a hospital. And when we do get sick, the price is outrageous. When my mom died, the cost for her two-week hospital stay totaled well over $100,000. Even with a medical degree, I could barely decipher the bills. Thankfully, she had great insurance and secondary insurance. Through my grief, I understood that we were lucky to be able to pay the remainder; the exorbitant cost of medical care causes half of US bankruptcies annually. One in five of us—including many families with young children—such as those with preemies who require prolonged stays in intensive care units, struggle to pay medical bills.11

In the US, the typical solution to health problems, both on an individual and population level, is to double-down on medical care. Problem is, usually, the vast sums of money we spend goes to care after we’re already sick. It’s like towing your car into the shop after the brakes have already failed and you’ve run into a ditch. The cost becomes a vicious circle. Because of the expense, Americans routinely forgo preventive care and don’t seek help until it’s a five-alarm emergency. Our cost-induced aversion to preventive care, however, only increases the cost of fixing what’s wrong when we do seek help. As Dr. Darrell Kirch, president and CEO of the Association of American Medical Colleges, the organization that represents all the accredited US medical schools and major teaching hospitals, said to me, “Good medical care doesn’t guarantee good health. There are other factors at work.”12

Meanwhile, the majority of the $3.5 trillion health-directed resources in the US—more than 95 percent—are spent on clinical care–related services.13 This includes doctor’s office visits, hospital stays, medications, imaging studies, laboratory testing, and procedures (i.e., biopsies, surgeries, etc.), nursing care facilities, and related administrative costs. What’s strange is our government spends absurd amounts of money on these services compared to every other developed country in the world, and still one in ten Americans does not have health coverage.14 America dedicates nearly twice as much of its economy to health care as the UK (17.9 percent US GDP versus 9 percent UK GDP), yet, unlike the British, we don’t provide basic free medical care for all.15 It’s like we’ve walked into a supermarket where the cashier charges us double for the same apples as everyone else, and ours are rotten.

For me as doctor, there’s one more point that’s truly shocking. Data shows that clinical care, as we currently provide it, isn’t actually making us much healthier. In fact, studies estimate that what happens at the doctor’s office and hospital accounts for only 10 to 20 percent of a person’s overall health status; it doesn’t significantly contribute to overall population health and well-being. Additionally, evidence shows spending more on medical care access and quality only improves preventable deaths by a slim 10 to 15 percent.16 Despite our massive investment in health care, numerous well-done studies paint the same picture over and over: the contribution of medical measures to the decline in mortality is questionable.17

These surprising findings are at the heart of this book. Our nation spends a fortune on health care, yet we remain remarkably unwell.

So if biomedical advances and expensive medical care aren’t making the difference to our health, what is? What would actually make us healthier?

Which brings us to the rabbits.

New Zealand white male rabbits develop heart disease much like humans if fed a high-fat diet. Today most people know that eating fried food and steaks daily is asking for trouble. But back in 1978, researchers were still trying to establish the relationship between high blood cholesterol and heart health. Dr. Robert Nerem and his team designed a straightforward experiment using what he calls “the standard rabbit model” to show the link.18 Over several months, he fed a group of rabbits the same high-fat diet. At the end of the study, he measured the animals’ cholesterol, heart rates, and blood pressure. As expected, the cholesterol values were all high and virtually identical to one another. The rabbits had similar genes and ate the same diet. Now they all seemed destined for a heart attack or stroke.

As the last step, Dr. Nerem needed to examine the rabbits’ tiny blood vessels. Looking through the microscope, he expected all the rabbits to show similar fatty deposits on the inside of their arteries. Instead, Dr. Nerem had a shock. As it turned out, there was a huge variation in the fatty deposits between the animals. One group of rabbits had 60 percent fewer deposits than the other. It made no sense. He recalls wondering, “What in the world could this be?” There was no clear biological explanation for these findings. He was staring down his microscope at a medical mystery.

Dr. Nerem and his team searched for clues. They looked again at the research design. Nothing unusual. But Dr. Nerem knew to keep looking. He said, “Sometimes there are things involved in a protocol that we don’t take into account.” So the research team looked at themselves.

A Canadian postdoc named Murina Levesque had recently joined the lab. Dr. Nerem remembers, “She was an unusually kind and caring individual.” When it became apparent that all the animals with fewer fatty deposits were under Murina’s care, the team dug deeper. They noticed that Murina handled the animals differently. When she fed her rabbits, she talked to them, cuddled and petted them. She didn’t just pass out rabbit kibble—she gave them love. As Dr. Nerem explains, “She couldn’t help it. It’s just how she was.”

Now a professor emeritus of bioengineering at Georgia Tech, Dr. Nerem says, “We were not social behavioral scientists,” but the team decided they could not ignore the findings of the social environment’s effect on physiology. The research group repeated the experiment, this time with tightly controlled conditions. They compared the arteries of one group of rabbits cared for by the new postdoc to the arteries of another group of rabbits cared for in the standard way. They found the same effect again and published these findings in the prestigious journal Science.19 Take a rabbit with an unhealthy lifestyle. Talk to it. Hold it. Give it affection. And many adverse effects of diet disappear. The relationship made a difference. But how?

Medical training teaches doctors to break the body down into disparate parts: organs, tissues, cells, and molecules. Physicians divide by specialty in this same way. There are doctors for every bit: heart, kidney, gut, bone, brain, and so on. This fragmented view stems from the underlying theoretical premise that disease arises from internal biological processes gone haywire. It is an exciting inner-world journey that has dominated medical thinking for the last century, and it is what I—and countless other medical doctors—spent all those years painstakingly studying.

But then there were the rabbits. These studies indicate something is missing in the traditional biomedical model. It wasn’t diet or genetics that made a difference in which rabbits got sick and which stayed healthy; it was kindness.

It turns out the rabbits were just the introduction to a much larger story. I call it the Rabbit Effect.

When it comes to our health, we’ve been missing some crucial pieces: hidden factors behind what really makes us healthy. Factors like love, friendship, and dignity. The designs of our neighborhoods, schools, and workplaces. There’s a social dimension to health we’ve completely overlooked in our scramble to find the best and most cutting-edge personalized medical care. Even having something that motivates us to get up and out of bed in the morning makes a difference to our physical well-being.

Because, as it turns out, being and staying healthy isn’t something that can be addressed through biomedical advances alone. Or by more and more spending on health care. Even the usual self-help directives—“Eat better! Work out! Get more sleep!”—will only get us so far. All these approaches overlook the critical social dimensions to ensuring sound minds and bodies. Ultimately, what affects our health in the most meaningful ways has as much to do with how we treat one another, how we live, and how we think about what it means to be human than with anything that happens in the doctor’s office.

This book will empower you to change your health. But not in the usual ways. I won’t give you a ten-step fitness plan or a two-week diet. That’s not what you need. That’s not going to make you healthier in the long run. Instead, I’ll take you with me through the halls of the hospital, invite you into the room with my patients to discover why they are sick and what might make them well. Together, we’ll investigate clinical puzzles that defy expectations, unearthing the hidden factors that determine who is sick and who is well, who will live and who will thrive. We’ll discuss stories from communities renowned for their longevity, and data from studies that turn conventional thinking on its head.

We’ll also explore the surprisingly strong connection between mental and physical health. Together let’s examine how that physiological link, in turn, is aggravated by hidden factors awry in our environment. In other words, to better understand why and how we get sick—and how individuals can boost health—we’ll look at the brain and body in the context of our day-to-day interactions. We’ll then zoom out to an aerial view and look at solutions that boost collective health for all of us. At the end of each chapter there is a tool kit that offers ideas for your own process of self-discovery.

None of this means I’m going to insist you see a therapist. Or try to convince you to take more pills. Instead, we’ll learn to pay attention to how symptoms, such as anxiety or depression or fatigue or pain, may reflect a red flag that something going on in your world needs attention. And how once we’ve addressed our own red flags, we can individually and collectively help others address theirs.

Ultimately, we will come to see how the larger ties that bind us—ties of love, connection, purpose—have ripple effects on our health and the world at large. And throughout the process, we’ll consider fundamental questions about how we live. I’ll ask you to examine your family, your relationships, your community, your neighborhood, your work, and your passions. I’m going to ask you to forget everything you think you know about health and wellness, and together we’ll open our minds to a new paradigm, a new way of thinking about how we live and what it means to thrive.

About The Author

Photograph © Agaton Strom

Dr. Kelli Harding is an assistant professor of psychiatry at Columbia University Medical Center. She is a diplomat of the American Board of Psychiatry and Neurology, as well as boarded in the specialty of psychosomatic (mind-body) medicine. Kelli works in the emergency room at New York-Presbyterian Hospital, and has appeared on Today, Good Morning America, NPR, The New York Times, Medscape, WFUV’s Cityscape, and US News & World Report.

Product Details

  • Publisher: Atria Books (November 3, 2020)
  • Length: 288 pages
  • ISBN13: 9781501184277

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Raves and Reviews

“A blending of free-flowing confessional prose and scholarly research . . . Amid the clanging political noise about Obamacare, Medicare, Medicaid, health insurance, and thieving pharmaceutical companies, Kelli Harding stands apart from the horde . . .”

– The Washington Post

“[A]n inspiring guide that will appeal to health enthusiasts fed up with the usual '10-step fitness plan or . . . two-week diet.' . . . Harding’s book will leave readers with much to ponder and . . . an encouraging rationale for treating others more kindly.”

– Publishers Weekly

“Readers will be inspired to make these manageable, life-altering changes.”

– Booklist

“[Offering] the kind of do-able and wise solutions that make for a better life, [Dr. Harding] illustrates the deep connections between stress—and the inflammatory response it evokes—and our physical and mental health. . . . She beautifully identifies kindness as an endlessly renewable resource—the light we all can shine on the lives of others and in so doing bathe in its grace ourselves.”

– New York Journal of Books

“[T]he most interesting [book on kindness] . . . personal, while also steeped in data . . . Harding [shows] how our interconnectedness helps us stay healthier . . . I couldn’t help tearing up.”

– New York Times Book Review

“An illuminating exploration of a new vision of the practice of medicine and health that demonstrates what our lives could be like if we targeted our ‘hidden factors of health,’ looked more to our social world for solutions to our health woes, and recognized how beneficial and transformative the use of kindness is . . . I give this book a glowing recommendation.”

– Psychiatric Times

“A beautifully written, inspiring book! The Rabbit Effect is truly eye opening and a joy to read. It illuminates vital public health research showing kindness in our day-to-day lives can make the world a healthier, happier place. I recommend this book highly for anyone who wants to live more healthfully.”

– Christy Turlington Burns, humanitarian and CEO of Every Mother Counts

“A wonderful demonstration of how our physical health is affected by the kindness we receive—and the kindness we give. Beautifully written and based on really hard science.”

– Lord Richard Layard, professor, London School of Economics, coauthor of The World Happiness Report

“Dr. Harding weaves together compelling clinical vignettes with fascinating medical evidence. This comprehensive, holistic view of health is critical, much needed, and absolutely convincing.”

– Arthur J. Barsky, MD, professor of Psychiatry, Harvard Medical School

“[A] blockbuster book. . . . Dr. Harding shows us that, by being compassionate, giving, and kind human beings, we can win the great rewards of vitality and longevity. Read this book! It will change your life.”

– Mindy Thompson Fullilove, MD, LFAPA, HonAIA, author of Urban Alchemy: Restoring Joy in America's Sorted-Out Cities

“In this brilliant and delightfully practical book, Dr. Kelli Harding unveils the hidden factors that determine our health and well-being. . . . The Rabbit Effect’s radical argument is that the most promising remedies for our biomedical problems will come from the social world, not the doctor’s office or pharmaceutical lab.”

– Eric Klinenberg, #1 New York Times bestselling coauthor of Modern Romance and author of Palaces for the People

“An inspiring, evidence-based and beautifully written exploration of the profound impact that love, connection and kindness have on our health. Harding's book should be required reading for all health practitioners and anyone with an interest in a living a longer, healthier and happier life.”

– Mark Williamson, PhD, director of Action for Happiness

“This book is fascinating because of Dr. Kelli Harding’s unique ability to combine stories with a deep understanding of the scientific foundation of the stories. This is an extremely compelling book, which will entertain, educate, and impact the readers.”

– Moshe Szyf, PhD, GlaxoSmithKline and James McGill Professor, Department of Pharmacology & Therapeutics, McGill University Medical School

“It’s utterly wonderful. Dr. Harding has reviewed the science on why community matters to individuals’ physical and mental health in a truly masterful manner, which will reach both scientific and lay audiences. I learned a great deal.”

– Laurence Guttmacher, MD, professor of Clinical Psychiatry, Clinical Medical Humanities, and Bioethics at the University of Rochester, School of Medicine & Dentistry

“Dr. Harding knows what our mental health needs. More Kindness! This book has a powerful message for us all—backed by ample research—and woven together with the warmth of an expert clinician.”

– Drew Ramsey, MD, assistant clinical professor of Psychiatry at Columbia University and author of Eat Complete

“When we first conducted the rabbit studies over 40 years ago, we never imagined the critical role that relationships play in health. I'm excited that those studies helped motivate this splendid book. Dr. Harding’s evidence-based exploration provides readers with a new way to think about human disease, one rooted in the importance of kindness and relationships. As stated in the Ecclesiastes proverb quoted in the book, a ‘faithful friend is the medicine of life.’”

– Robert M. Nerem, PhD

“Blest are those patients cared for tenderly and wisely by Dr. Kelli Harding. Blest, too, are those who read her book and absorb it into their physical and spiritual lives.”

– Colman McCarthy, journalist and peace teacher

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