Objective: To estimate the 12 month prevalence of DSM-IV disorders in New Zealand, and associated interference with life and severity.
Method: A nationally representative face-to-face household survey carried out in 2003-2004. A fully structured diagnostic interview, the World Health Organization World Mental Health Survey Initiative version of the Composite International Diagnostic Interview (CIDI 3.0) was used. There were 12,992 completed interviews from participants aged 16 years and over. The overall response rate was 73.3%. In this paper the outcomes reported are 12 month prevalence, interference with life and severity for individual disorders.
Results: The prevalence of any disorder in the past 12 months was 20.7%. The prevalences for disorder groups were: anxiety disorders 14.8%, mood disorders 7.9%, substance use disorders 3.5%, eating disorders 0.5%. The highest prevalences for individual disorders were for specific phobia (7.3%), major depressive disorder (5.7%) and social phobia (5.1%). Interference with life was higher for mood disorders than for anxiety disorders. Drug dependence, bipolar disorder and dysthymia had the highest proportion of severe cases (over 50%), when severity was assessed over the disorder itself and all comorbid disorders. Overall, only 31.7% of cases were classified as mild with 45.6% moderate and 22.7% serious.
Conclusions: Compared with other World Mental Health survey sites New Zealand has relatively high prevalences, although almost always a little lower than for the US. For all disorders, except specific phobia, interference with life was reported to be moderate, on average, which has lead to less than a third of cases being classified as mild. Most people who have ever met full DSM-IV criteria, including the impairment criterion, and who experience symptoms or an episode in the past 12 months find that their disorders impact on their lives to a non-trivial extent.