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Is Mental Illness the Rule Rather Than the Exception?

A new study finds only 17 percent of people avoid diagnoses over the long term.

When we hear about the number of people who struggle with psychiatric conditions, the most common quote is 1 in 5 for any given year. This statistic comes from several reports issued over the years by the Surgeon General’s office and the Substance Abuse and Mental Health Services Administration (SAMSA).

To critics, this number already seems unbelievably high. But new research will fuel the controversy further, and it comes from one of the most famous long-term mental health studies ever done. The Dunedin Study has followed slightly more than 1,000 individuals from New Zealand for 35 years, starting when the subjects were only 3. The data from this study have led to a number of publications over the years and several major headlines. The goal of the latest effort was to identify factors related to people who have managed to remain free of all psychiatric diagnoses during the entire study interval. What was surprising was just how small this group turned out to be.

The 1 in 5 ratio returns in this study, but to signify the number of individuals who, across the full 35-year period, did not meet any criteria for a psychiatric disorder at any of the multiple assessment points. In fact, only 17 percent of the sample qualified for this designation. Far more common were individuals who over the decades had occasional times when they met criteria for one or two disorders—most commonly anxiety, depression, and substance abuse—although those episodes were often temporary.

To return to the original aim of this study, enduring long-term mental health turned out not to be significantly related to some of the expected factors, such as wealth, physical health, or even intelligence, but rather to certain early temperament and personality factors that could be identified when the subjects were as young as three years old, such as being more social, being less emotionally reactive, and having higher levels of self-control. Not having family members with psychiatric disorders was also predictive.

One can already feel the eye rolling and hear the negative reactions by some to this research. Much of the concern will likely surround medication overuse and/or the stigma that would be predicted to follow such an increased number of individuals with a diagnosed psychiatric condition. Both are clearly important issues deserving of comment. Regarding medication, the study did not go into details about its sample, but the report clearly gives the impression that medications were not overly common, with many people reporting episodes of depression or anxiety which resolved without pharmacological support. Even allowing for the somewhat fuzzy logic that we should deny the existence of a medical problem because we don’t like the way it’s treated, there is reason to be optimistic that the use of psychiatric medications is coming into more balance with other types of interventions as well as important wellness and health promotion activities.

As far as the stigma goes, there is a good argument to be made that a more inclusive perspective of mental illness that actually acknowledges how many of us may struggle from time to time is far less stigmatizing than a view which restricts psychopathology to an isolated few, while the rest of us do all we can to convince others that there’s “nothing to see here.”

About three years ago, I wrote a post here asking, “What if We All Got Mentally Ill Sometimes?” In light of these new data and other studies like it, the question begs asking again.

At a recent conference, I was looking around the room and noticing what a large percentage of attendees were wearing glasses. Thank goodness nobody had convinced them that they should have just accepted their visual difficulties as “normal” with no intervention needed other than a good squint.

Copyright by David Rettew

Follow David Rettew on Twitter at @PediPsych

LinkedIn Image Credit: pixelheadphoto digitalskillet/Shutterstock


Schaefer JD, Caspi A, Belsky DW, et al. (2017). Enduring mental health: Prevalence and prediction. Journal of Abnormal Psychology 126: 212-224.

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