DUKE (US)—A long-term tracking study of more than 1,000 New Zealanders from birth to age 32 suggests that people vastly underreport the amount of mental illness they’ve suffered when asked to recall their history years after the fact.
“If you start with a group of children and follow them their whole lives, sooner or later almost everybody will experience one of these disorders,” says Terrie Moffitt, the Knut Schmitt-Nielsen professor of psychology and neuroscience at Duke University.
Because self-reporting from memory is the basis for much that is known about the prevalence of mental disorders, anxiety, depression, and substance dependency may actually be twice as high as previously believed, according to new research.
Moffitt says longitudinal studies like this one—the Dunedin Study—that track people over time are rare and expensive.
Jane Costello, professor of medical psychology at Duke, runs a similar project, the Great Smoky Mountains Study, which tracked 1,400 American children from age 9-13 into their late 20s and found similar patterns.
“I think we’ve got to get used to the idea that mental illness is actually very common,” Costello says. “People are growing up impaired, untreated, and not functioning to their full capacity because we’ve ignored it.”
The latest analysis from the Dunedin Study found 41 percent of the age range had experienced clinically significant depression. The study also reported a lifetime rate of alcohol dependence between ages 18 and 32 at nearly 32 percent.
Guidelines published by the American Psychiatric Association that set the bar for defining what is and isn’t a treatable illness are currently being revised by a rewriting of the authoritative Diagnostic and Statistical Manual of Mental Disorders (DSM).
Given the findings of recent longitudinal studies, the stringency of the diagnostic criteria may need to be reconsidered, says Moffitt, who is on the committee writing the new DSM-V standards.
“Researchers might begin to ask why so many people experience a disorder at least once during their lifetimes and what this means for the way we define mental health, deliver services, and count the economic burdens of mental illness,” Moffitt argues.
At the very least, maybe these findings can help reduce the stigma against mental illness and mental health care, Moffitt adds. New Zealand, for example, has begun a new campaign of public service announcements featuring sports heroes saying they’ve experienced mental health issues.
“If we’re serious about this problem, we need to get serious about preventing it,” Costello says. “We do know a lot more about prevention now.”
The Dunedin Study findings appear online in the journal Psychological Medicine. The work was supported by the New Zealand Health Research Council, the US National Institutes of Health, and the UK Medical Research Council. Psychologists at Duke University and their colleagues from the United Kingdom and New Zealand participated in the research.
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