On a recent visit to West Hampstead I passed a woman with a dog. She was mumbling something to herself, to the dog, or to no one—I couldn’t tell. She didn’t notice me. As I drew near, she snapped out of her reverie. Sorry, I’m a little crazy,” she said in a small voice.

Who isn’t? I called back, without turning. I didn’t expect her to hear me, but she answered.

“Thank you.”

I still think about this woman. Was she embarrassed? Apologetic? Matter-of-fact? Or maybe just vividly, unselfconsciously earnest the way kids can be, and also the crazy? And what did she thank me for?

It’s a symptom of our time. Consider how we think and talk about mental health and mental illness: shot through with ambivalence. Over the past few years, we’ve seen a big push from governments, charities, and the Royals to put mental health on an equal footing with physical health. A slew of campaigns have sprung up to raise awareness of the scale of the problem and fight the stigma attached to it. Major efforts have been thrown into depersonalizing mental disorder, encouraging the afflicted to talk and their friends, families, and employers to empathize.

Mental illness is a biological fact beyond anyone’s personal control. It’s in your brain, and you can’t just snap out of it.

One of the underlying messages of these campaigns is that mental illness is wide-ranging, affecting 1 in 4 of us. Similar to cancer and diabetes, depression comes down to some inherent glitch in the system, a matter of aberrant biology. Just like the cells of diabetics fail to convert glucose into energy—which leads to a buildup of sugar in the bloodstream—the brains of depressives, the theory goes, come with faulty wiring that inhibits mood regulation.

This runs counter to another, seemingly more insidious, idea — that mental breakdown is not a real problem but a character flaw, a pretend suffering, an elaborate excuse for people who simply lack the discipline or mental fortitude to suck up and carry on.

It is partly this belief that fuels the stigma. Public campaigns strive to root it out by reframing mental illness as a biological fact beyond anyone’s personal control. Put bluntly: It’s in your brain, and you can’t just snap out of it.

The model of mental distress as a brain disease has garnered the support of eminent public figures, from comedians Ruby Wax and Stephen Fry to Tony Blair’s former spokesman Alastair Campbell.

“Nobody ever gets blamed for getting physical illness,” writes Campbell, “so why on earth do we still talk about depression like it is the fault, and the lifestyle choice, of the depressive?”

In a widely praised documentary he made for the BBC, Stephen Fry similarly talks about his bipolar disorder, which, he says, he had to accept as incurable and learn to live with.


The Problem with Anti-Stigma Campaigns

On the surface, we’ve made big strides educating the public and stamping out the stigma. A 2014 report on Time to Change — the most ambitious mental health campaign in the UK, which has run since 2009 thanks to more than £44 million pledged in funding — found increased tolerance toward people struggling with psychological distress.

More than 70 percent of respondents agreed that people who suffer from mental illness should be afforded the best possible care. A similarly high number said the afflicted should not be held accountable for their condition.

To many, such findings hail a dramatic positive shift in the general public’s acceptance of otherness. But some researchers suspect that the figures don’t tell the whole story. Recent evidence, for example, suggests that while mental health campaigns may have changed people’s minds, they have failed to move their hearts.

A number of credible studies have found that explaining mental distress in disease terms does promote tolerance, but only superficially. If you perceive mental illness as a brain disorder, these studies show, you are more likely to say nice things about people with a diagnosis and you are less likely to judge them.

At the same time, however, you are also more likely to want to avoid interacting with them and to rate them more prone to violence, less able to make sound judgements about their lives, and less likely to recover. This disparity between what people say and what they believe has led researchers to conclude that campaigns of the disease-like-any-other type may reinforce the stigma rather than remove it. How can we explain this?

Sheila Mehta, a psychology professor at Auburn University, conducted an experiment in which students were paired with undercover research assistants who had to complete a task while the students gave them feedback through electric shocks. When the students were told that their partner had a brain disease affecting his biochemistry, they blamed him less when he made errors and rated the shocks they administered as less painful than a control group that hadn’t been given the disease explanation.

We may not blame people when they break down; instead, we pity them. We patronize them. We are compassionate and understanding, but only at an appropriate distance.

This outward kindness, however, was at odds with the students’ behavior. The disease model group actually gave harsher shocks, up to 170 percent more intense, than the control group. Here’s how Mehta explains her findings:

The disease view may incline us toward an awareness that we ought to have generous feelings toward the afflicted but this view may also induce us to view those with mental disorders as set apart from humanity. (….) Biochemical aberrations make them almost a different species.

Put another way, a disease like any other is still a disease. Despite their best intentions, mental health campaigns that cast psychological conditions as brain diseases may have merely subbed biological pathology for personal responsibility. As a result, we may not blame people when they break down; instead, we pity them. We patronize them. We are compassionate and understanding, but only at an appropriate distance.

Instead of encouraging inclusion, the disease view of mental illness may be fueling inequality. Instead of building a bridge, it may be driving an ever-wider wedge between us-the-healthy and them-the-sick, us-the-normal and them-the-mental.

This is why, I’m beginning to think, the woman with the dog thanked me. Despite her crazy talk, I spoke to her as if she were just another ordinary person going about her ordinary business. As far as I was concerned, she had every right to stand tall and inhabit without apology her place in the order of things.

This wasn’t tolerance on my part. When I blurted out that everyone is essentially crazy, I was simply putting in layman’s terms what one of the most extensive studies on mental health had already revealed; namely, that for any one of us, mental illness may be lurking just around the corner.

It’s More Common Than We Thought

If I asked you how many people you think would have a diagnosable disorder at some point in their life, odds are you’d say 1 in 4. In the UK, this statistic is seemingly tacked onto everything related to mental health—every news piece, every government report, every tube billboard, and every charitable campaign.

What’s interesting, though, is that this figure comes not from any conclusive evidence on the prevalence of mental illness but from surveys conducted by the UK Office of National Statistics that asked respondents if they had experienced distressing symptoms over the previous week.

The problem with such surveys is that the way you feel on any given week may hold little clue about your mental state in general. Despite their rendering in popular imagination, mood disorders don’t knock you into a bottomless pit where you sit and stare, eyes glazed over, into nothingness. They often vacillate through ups and downs: catatonic stillness followed by frenetic activity or even calm.

If someone who was normally struggling took the survey in an unusually good month, that person would likely report no symptoms or downplay their severity, and would thus be counted as asymptomatic. Ditto for people in denial of their condition or those who hide it, reluctant to spill intimate details to strangers.

But despite such obvious methodological flaws, the 1 in 4 figure stuck. To anyone concerned with mental health, it must have seemed about right — high enough to render it of public concern yet still low, as pathologies are.

What we think of as the madness of the few may turn out to be the secret we all share.

Meanwhile, other studies existed, albeit few and far between, that tried to quantify the scale of mental illness. Some were better designed and therefore less biased, yet they failed to make much of an impact.

One used civil registry data to track 5.6 million Danes between 2000 and 2012 and estimated that roughly 1 in 3 received psychiatric help during that period. This, mind you, in the world’s (allegedly) happiest country, in the presence of free universal health care, and not counting people in private therapy, on medication or those who sought no treatment at all.

Other data came from the U.S. National Comorbidity Survey, the country’s first large-scale study of the prevalence of mental illness. Between 1990 and 1992 more than 8,000 Americans were interviewed, then reassessed 10 years later, followed by a batch of 9,282 new participants in 2001 and 2002.

About 50 percent of all respondents met the criteria for mental illness over the course of the study. Although high in comparison to previous estimates, this figure was likely still too low because of design limitations — from recall failure (most of us forget or misremember things over time) to selective participation (the people with the most severe symptoms also tend to be the ones most unwilling to disclose their medical histories).

A Rare Disease or a Social Epidemic?

Then in 2016, Terrie Moffitt and Avshalom Caspi, a research team from Duke University, did their own estimation of the prevalence of mental disorders. Moffitt and Caspi are widely recognized as pioneers in the field of gene-environment interaction, which took off in the late 90s with the spread of genome sequencing tools.

Before their momentous meeting on a river cruise along the Mississippi, Caspi was looking at how childhood personality and family environment shape people’s life trajectories. Moffitt, meanwhile, was puzzling out the gene variations that made someone prone to extremes such as criminality and clinical depression.

Eventually the two decided to join forces and wield the tools of their respective disciplines — hers: clinical psychology, neuroscience, and genetics; his: sociology, epidemiology, and behavior studies — to take on some of the biggest questions in human development. Drawing on staggering amounts of new tools and data, they are beginning to map out the complex dance of biology and psychology, of nature and nurture, as it plays out throughout human life.

When they decided to measure the true scale of mental illness, Moffitt and Caspi had an additional advantage over most researchers. Moffitt is associate director of the Dunedin Multidisciplinarian Health and Development Study, one of the few research projects that track people from late childhood, when most mental disorders first manifest themselves, well into midlife. The project began in the early 70s by following 1,037 babies born in the span of one year in Dunedin, a town in New Zealand known as “the Edinburgh of the South” because of its Scottish heritage.

Now in their forties, the study’s subjects continue to show up for assessments every few years—flying, driving, or walking to the researchers’ offices for a day full of personal interviews, surveys, physical exams, blood samples, retinal imaging, and other tests designed to poke into every nook and cranny of their lives, from their deepest despairs to their latest caries.

Most longitudinal studies have high dropout rates. The average rate is 20 percent, but it can easily go up to 70 percent for longer follow-up periods as participants get busy, move away, or simply disengage. Not the Dunedin subjects. More than four decades after the study began, an astonishing 95 percent of the surviving original cohort still show up for assessments. It’s this uncommon loyalty to the project that makes Moffitt and Caspi’s research so remarkable. Not only have they amassed a wealth of data free from much dropout-related bias, but by earning the goodwill of their subjects, they’ve also managed to capture deeply personal details that other studies may have trouble eliciting.

Having a front seat to people’s lives unfolding has yielded a trove of insights into human health and behavior, such as the finding that people are more likely to become obese the longer they sleep on weekends than weekdays. Another revelation: For every hour children spend in front of the TV, their risk of criminality later in life jumps by 30 percent.

To probe the prevalence of mental disorders, Moffitt and Caspi had experienced psychologists interview the subjects every few years between the ages of 11 and 38. When asked about their symptoms over the past year, 408 (41.3 percent) of the respondents reported episodes of depression, anxiety, or substance use on more than three assessments; 409 (41.4 percent) reported on one or two assessments; and only 171 — 17.3 percent — reported being symptom-free throughout. Of all the participants, the overwhelming majority had met the criteria for mental disorder at least once between late childhood and midlife.

Mental illness, in other words, turned out to be far more common than researchers had thought—so much so that it no longer looked like an exception, a deviation from the norm. It was the norm.

This can be hard to square with widely held beliefs. Accepting the Dunedin study’s results would put the prevalence of mental disorders at roughly 83 percent — meaning not 1 in 4, not even 1 in 2, but 1 in 1.2.

Surely something about the study must be off. Were the subjects overly sensitive in the first place? Was the definition of mental illness too liberal? Could it be that petty miseries got lumped together with legitimate ills?

Moffitt and Caspi showed that in terms of general health and past-year incidence of mental distress, the Dunedin sample was similar to the wider population of New Zealand as well as the U.S. They based their diagnoses on the Diagnostic and Statistical Manual of Mental Disorders (DSM) — the standard (if increasingly controversial) tool used by clinicians, researchers, and drug-regulation agencies around the world.

Granted, the 83 percent lifetime prevalence of mental illness that Moffitt and Caspi found reflects a range of symptoms and severities. The subjects diagnosed at more than three assessments displayed a wider range of disorders — such as PTSD, ADHD, schizophrenia, and mania — that were rare or nonexistent in subjects diagnosed only once or twice. This more chronic group also had a higher chance of suffering from more than one disorder simultaneously and their actual impairment was more serious.

The milder cases, in comparison, had relatively brief episodes of anxiety, depression, and substance use. But while it’s tempting to dismiss them as small matter, they are anything but. Moffitt and Caspi don’t share specific figures, but according to a NHS clinician I spoke to, a so-called mild episode typically lasts 23 days.

This number has been echoed by recent economic studies, which estimate that in the UK, mental health issues cause productivity losses for 21 to 30 days per person per year. Furthermore, when Moffitt and Caspi compared the mildly affected to those never diagnosed, they found that the latter enjoyed significantly higher life satisfaction and social and economic status, as well as more education and better relationships.

What Does It All Mean?

What used to look like a rare disease may, in fact, be a social epidemic — or, rather, human experience. It also means that what we think of as the madness of the few may turn out to be the secret we all share.

This is not to say that genetic risks and brain chemistry don’t matter, or that a four-week bout of depression exacts the same toll as one that puts you in the psych ward. But when it comes to the human mind, things defy the simple and often deterministic explanations of biology. The boundaries are blurry where normal ends and crazy begins. Mental health, it turns out, is not a given, and mental illness is not a genetic verdict.

Perhaps the most fascinating — and foreboding — possibility suggested by the Dunedin study is that ours is a mad world. Today you don’t need bad genes or a rotten childhood to go crazy; living in what journalist Sebastian Junger called “an overfed, malnourished, sedentary, sunlight-deficient, sleep-deprived, competitive, inequitable, and socially-isolating environment” may be enough. Being human may be enough.


Acknowledgments

Huge thanks to Chris Messina, Brad Feld, Jonny Miller, Rory Sutherland, Joshua Davidson, Chris Guillebeau, and Don Krueger for reading early drafts of this article and encouraging me to publish it.

I am also grateful to the people who shared their thoughts and stories and inspired me to keep up the research when I was about to give up: Sean Percival, Srinivas Rao, Sarah Jane Coffey, Rand Fishkin, Amanda Gelender, John Romaniello, Joe Scarboro, Evgeny Shadchnev, Dan Bladen, Danny King, IanSanders, and Paul Smith.