Mental Illness May Be More Common Than We Know, but It Is Temporary for Most Individuals

Mental illness may be more common than we know, but it is temporary for most individuals

A longitudinal research conducted in New Zealand suggests mental illnesses are so common that almost everyone will develop at least one diagnosable mental disorder at some point in their lives. Most of these people will never receive treatment, and their relationships, job performance and life satisfaction will likely suffer. Meanwhile the few individuals who never seem to develop a disorder may offer psychology a new avenue of study, allowing researchers to ask what it takes to be abnormally, enduringly, mentally well.

Epidemiologists have long stated that the lifetime prevalence rates for mental illnesses are 20 to 25 percent, experiencing psychological distress severe enough to impair functioning at work, school or in their relationships. Extensive national surveys, conducted from the mid-1990s through the early 2000s, suggested that a much higher percentage, close to half the population, would experience a mental illness at some point in their lives.

These large surveys involve thousands of participants representative of the U.S. in age, sex, social class and ethnicity. However, they are also retrospective, which means they relied on survey respondents’ accurate recollection of their experiences in the past.

In a recent study, published earlier this year in the Journal of Abnormal Psychology, took a different approach to estimating disease burden. Instead of requring participants to recall from their memory, the researchers closely followed one generation of New Zealanders, all born in the same town, from birth to midlife.In-depth check-ins were conducted every few years to determine the state of their mental health in the previous year.

The researchers concluded that if you follow people over time, and screen them regularly using simple, evidence-based tools, the percentage of people who develop a diagnosable mental illness at any point in their lives increase to well over 80 percent. Only 17 percent of the participants in the research did not develop a disorder, at least briefly, by middle age. They also highlighted the true proportion could be lower as there were periods between the assessments where they were not assessed.

According to Jonathan Schaefer, the first author of the paper, "Our study shows that you are more likely to experience a bout of mental illness than you are to develop diabetes, heart disease or any kind of cancer whatsoever—combined. These findings have been corroborated by data from other similar cohorts in New Zealand, Switzerland and the U.S".

Jonathan Schafer pointed out that it is also also a faulty assumption that you will have a psychological disorder if you develop a psychological disorder.. The newest research suggests, for the most common psychological complaints, this is simply not true. “A substantial component of what we describe as disorder is often short-lived, of lesser severity or self-limiting,” says John Horwood, a psychiatric epidemiologist and director of the longitudinal Christchurch Health and Development Study in New Zealand. (Horwood has found that close to 85 percent of the Christchurch study members develop a diagnosable mental illness by midlife).

This may be a useful message to spread. According to Jason Siegel, a professor of social psychology at Claremont Graduate University, people tend to be more sympathetic and helpful when they believe that a friend or co-worker’s health problems are temporary.

And individuals with mental illness need support. Even short-lived or self-limiting disorders can wreak havoc on a person’s life. To be classified as having a disorder, “an individual typically has to meet fairly stringent symptom criteria,” Horwood says. “There needs to be substantial impairment of functioning.”

To some, though, the new statistics on mental illness rates can sound a lot like the overmedicalization of “normal” human experience. Advocates for individuals with mental health concerns tend to disagree with this perspective. “I’m not at all surprised by these findings,” commented Paul Gionfriddo, president of Mental Health America, a national advocacy group. His organization views mental illnesses as common, “though not always enduring.” Three years ago Mental Health America launched a Web-based tool to allow individuals to discreetly screen themselves for possible psychological disorders. Since then over two million people have used the tool, with over 3,000 people a day now logging on to determine if they may have a condition that could benefit from treatment.

In the New Zealand cohort, participants with enduring mental health were significantly different in two aspects. First, they had little to no family history of mental illness and, second, they tended to have what can be classified as “advantageous” personalities. As early as age five, individuals who would make it to midlife without an episode of mental disorder tended to display fewer negative emotions, get along better with their peers, and have greater self-control. Furthermore, these individuals were not any smarter, richer, or physically healthier than their peers, at least in childhood.

Ultimately, the most important suggestion from the newest research is that mental health concerns may be nearly universal. Acknowledging this universality may allow us to finally devote adequate resources to screening, treating and preventing mental illnesses. It may also help us go easier on ourselves and our loved ones when we, inevitably, hit our own rough patches in the road.


Schaefer, J. D., Caspi, A., Belsky, D. W., Harrington, H., Houts, R., Horwood, L. J., ... & Moffitt, T. E. (2017). Enduring mental health: Prevalence and prediction. Journal of abnormal psychology, 126(2), 212.