An international study suggests that the prevalence of anxiety, depression and substance dependency may be twice as high as the mental health community has been led to believe.
Duke University psychologists Terrie Moffitt and Avshalom Caspi and their collaborators from the UK and New Zealand say that it depends upon how one goes about measuring.
The researchers tracked more than 1,000 New Zealanders from birth to age 32, and came to the conclusion that people vastly underreported the amount of mental illness they had suffered, when asked to recall their history years after the fact.
However, said the researchers, 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.
According to Moffitt, longitudinal studies like the Dunedin Study in New Zealand, in which people are tracked over time, are rare and expensive.
"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.