Â
Mental health charities and campaigners typically claim that one in four of us will experience a mental illness at some point in our life-times. This prompts disbelief in some quarters. The rates can’t possibly be that high, so the argument goes, there must be something wrong with the figures. A new study led by Terrie Moffitt confirms that ‘Yes’, there is something wrong with the one in four figure – it should be one in two!
Previous estimates for the prevalence of mental illness are largely based on retrospective surveys. People are typically asked whether they’ve experienced any mental illness in the last year or at any point in their lives. The problem with this approach is that people forget or prefer not to mention a bout of illness that happened a long time ago.
Moffitt’s new study avoided this problem by using a longitudinal, prospective design. Over 1000 people born in Dunedin in New Zealand between 1972 and 1973 were assessed four times between the ages of 18 and 32 by clinically trained interviewers using standard (DSM; Diagnostic and Statistical Manual) psychiatric criteria.