Abstract
Objective: To assess the prevalence, symptom severity, functional impairment and treatment of major depressive episodes in the New Zealand population, in light of recent criticism that depression is ‘over-diagnosed’, especially in community surveys.
Method: Nationally representative cross-sectional household survey of 12 992 adults (aged 16+): The New Zealand Mental Health Survey 2003/4. 12-month major depressive episode measured in face-to-face interviews with the Composite International Diagnostic Interview (CIDI 3.0).
Results: The 12-month prevalence of major depressive episode (MDE) was 6.6% for the total population, with decreasing prevalence with increasing age, and higher prevalence in females (8.1% versus 4.9% in males). Fewer than 10% of 12-month episodes were classified on a symptom severity rating scale as mild, and 69% of all episodes were accompanied by severe impairment in at least one domain of functioning. Only a third of those with severe impairment received treatment in the mental health sector, and half saw a general medical practitioner.
Conclusion: These results offer little support for the suggestion that depression is over-diagnosed and over-treated, and that current diagnostic thresholds allow the inclusion of too many mild episodes in community surveys.
Acknowledgements
The survey was carried out in conjunction with the World Health Organization World Mental Health (WMH) Survey Initiative. We thank the WMH staff for assistance with instrumentation, fieldwork and data analysis. WMH publications are listed at http://www.hcp.med.harvard.edu/wmh/.
Other members of the NZMHS research team are: Magnus McGee, Joanne Baxter, Jesse Kokaua, Te Kani Kingi, Rees Tapsell, Siale Foliaki, David Schaaf, Mason Durie, Colin Tukuitonga and Chris Gale.
We thank the Kaitiaki Group and Pacific Advisory Group for their input and support for this survey and we thank all the participants.
Declaration of interest: Te Rau Hinengaro: The New Zealand Mental Health Survey (NZMHS) was funded by the Ministry of Health, the Alcohol Advisory Council of New Zealand and the Health Research Council of New Zealand. These activities were supported by the US National Institute of Mental Health (R01MH070884), the John D. and Catherine T. MacArthur Foundation, the Pfizer Foundation, the US Public Health Service (R13-MH066849, R01-MH069864, and R01-DA016558), the Fogarty International Center (FIRCA R01-TW006481), the Pan American Health Organization, Eli Lilly and Company, Ortho-McNeil Pharmaceutical, GlaxoSmithKline, and Bristol-Myers Squibb.