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Keywords:

  • adult;
  • cross-sectional study;
  • epidemiology;
  • ethnic group;
  • mental disorder

Objective:  To estimate the lifetime prevalence and projected lifetime risk at age 75 years of DSM-IV disorders in New Zealand.

Method:  A nationwide face-to-face household survey carried out in 2003–2004. A fully structured diagnostic interview, the World Health Organization 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 lifetime prevalence and projected lifetime risk at age 75 years.

Results:  The lifetime prevalence of any disorder was 39.5%. The lifetime prevalences for disorder groups were: anxiety disorders, 24.9%; mood disorders, 20.2%; substance use disorders, 12.3%; and eating disorders, 1.7%. The prevalences for all disorders were higher in the younger age groups. Females had higher prevalences of anxiety, mood and eating disorders compared with males; males had higher prevalences of substance use disorders. The estimated projected lifetime risk of any disorder at age 75 years was 46.6% with the median age of onset being 18 years. Adjustment for age, sex, education and household income did not remove all differences between Māori and the composite other ethnic group in the risk of disorder (hazard ratio = 1.1–1.4). After adjustment, hazard ratios for Pacific people ranged from 0.8 to 2.5.

Conclusions:  These results confirm those of other studies: mental disorders are relatively common and tend to have early onset. Females are more likely to experience anxiety, mood and eating disorders than males, who experience more substance use disorders. Adjustment for socioeconomic factors and demography does not explain all ethnic differences, although remaining differences are small relative to cohort and even sex differences.