DURHAM, N.C. -- The prevalence of anxiety, depression and substance dependency may be twice as high as the mental health community has been led to believe.
It depends on how one goes about measuring.
Duke University psychologists Terrie Moffitt and Avshalom Caspi and colleagues from the United Kingdom and New Zealand used a long-term tracking study of more than 1,000 New Zealanders from birth to age 32 to reach the conclusion that people vastly underreport the amount of mental illness they've suffered when asked to recall their history years after the fact.
But such self-reporting from memory is the basis of much of what we know about the prevalence of anxiety, depression, alcohol dependence and marijuana dependence. Longitudinal studies like the Dunedin Study in New Zealand that track people over time are rare and expensive, Moffitt said.
"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," said Moffitt, the Knut Schmitt-Nielsen professor of psychology and neuroscience at Duke.
The Great Smoky Mountains Study, a similar effort based at Duke, has tracked 1,400 American children from age 9-13 into their late 20s and found similar patterns, said Jane Costello, a professor medical psychology at Duke who runs the study.
"I think we've got to get used to the idea that mental illness is actually very common," Costello said. "People are growing up impaired, untreated and not functioning to their full capacity because we've ignored it."
The prevalence of mental illness has been hotly debated by policy makers and mental health providers for many years. The pharmaceutical and health insurance industries also have a stake in the debate, Moffitt said.
The best retrospective studies, the US National Comorbidity Surveys (NCS) and the New Zealand Mental Health Survey, have found the incidence of depression from
|Contact: Karl Leif Bates|