Mental illness: does it really affect one in five?

That number can go up or down depending on our definition of 'illness'


“One in five Canadians experiences a clinical mental illness and many more struggle with stress or grief.”—Globe and Mail, 02/07/2012

One in five of us has or will suffer from a mental illness: for years, we’ve peppered our news stories, health pamphlets, and advocacy campaigns with this statistic about the goings on in our heads. There are even entire mental health websites dedicated to it, such as OneInFive.ca courtesy of Dalhousie University.

It’s a number that knows no boundaries. In the U.S., a new national report found that one-fifth of American adults experienced mental illness in the past year.

So how do we know that a cool 20 per cent of us suffer from a mental health condition?

In Canada, Science-ish traced the recent origins of this bit of wisdom about our national head troubles back to the statistics page of the Centre for Addiction and Mental Health: “1 in 5 Canadians will experience a mental illness in their lifetime.” They footnote a 2002 “Report on Mental Illnesses in Canada” by the Public Health Agency of Canada, which also published a 2006 update on mental health—featuring our favourite statistic.

The health agency’s key informant? “Previous Canadian studies.” In particular: A 1996 study of  Ontarians that showed almost one in five (18.6 per cent) had one or more of the disorders measured, and an even older 1988 study, which looked at Edmontonians over a six-month period, and found 17.1 per cent experience a psychiatric disorder—again, a little less than one in five.

To find out more about this figure, Science-ish contacted Dr. Scott Patten, a physician who researches the epidemiology of mood disorders at the University of Calgary. “The ‘one in five during their lifetime’ idea has had a certain staying power. It has been repeatedly referenced in national reports in Canada, and continues to be.”

Dr. Patten has been investigating the topic for a forthcoming paper in the Canadian Journal of Psychiatry, entitled, “Is Mental Health in the Canadian Population Changing Over Time?” and has seen 20 per cent figure used around the world. While the Canadian iteration rests on rather limited data, Dr. Patten underscored how difficult it is to put a yardstick up to mental illness anyway. “You cannot directly measure the proportion of people who have a mental illness in their lifetime since any sample that is representative of the population will have young people who may develop an illness in the future, so such figures are typically educated guesses,” he explained. Also, most mental illnesses have fuzzy boundaries. “A lot of specific phobias are very common, like fear of snakes, but of questionable significance, and most conditions exist on a spectrum rather than fitting into discrete categories.”

For statistical purposes, those ephemeral ailments end up being forced into boxes. So, Dr. Patten says, “If you are depressed for two weeks after the death of a loved one, the Diagnostic and Statistical Manual of Mental Disorders says you have bereavement, which is not a mental disorder, but if you have the same symptoms of the same duration after losing your job or being diagnosed with a severe illness, it says that you do have a mental disorder.”

Still, prevalence rates have been climbing in recent years. When Dr. Patten was in medical school in the early- to mid-1980s, for example, only one in ten Canadians were afflicted. Now, as we know, it’s one in five. In Europe, the number is even higher: 38 per cent have a mental disorder in any given year. This raises some questions: are we crazier now than in the past, and are Europeans more mentally ill than North Americans?

Dr. Patten says the changing rates of mental illness are related to changing definitions and study methodologies. For example, “The European researchers commented that the apparently increasing prevalence is due to the fact that more recent studies have included much larger lists of disorders, accounting for the extremely large proportion,” he explained. The same phenomenon has taken place in the U.S. over time, and some fear that with the updated version of the Diagnostic and Statistical Manual (DSM-5) coming out, the number is poised to surge.

There are a few ways to look at the one in five, Dr. Patten figures. Some believe that advocacy groups and charities cherry-pick and inflate these statistics to emphasize the importance of mental health conditions. Others, that it’s an accurate best guess since mental health issues are the most common of health issues. The most cynical view, he says, is that “by incorporating more and more conditions and claiming higher and higher prevalence, normal life experiences are being malevolently re-branded as medical issues.”

Then, how many of us are really mentally ill? Coming up with a number is as tricky as describing what’s going on in your noggin. As Dr. Patten puts it, “In psychiatry, we don’t have any really solid, objective way of defining these things, so the facts can’t be entirely freed from values and interpretations.”

Thank you to reader Andrew Phillips of Ottawa, Ontario for writing in about the “suspicious” one in five statistic.

Science-ish is a joint project of Maclean’s, The Medical Post, and the McMaster Health Forum. Julia Belluz is the associate editor at The Medical Post. Got a tip? Seen something that’s Science-ish? Message her at julia.belluz@medicalpost.rogers.com or on Twitter @juliaoftoronto