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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.

Objective: The aim of the present study was to compare two versions of the Kessler 10-item scale (K10), as measures of population mental health status in New Zealand., Method: A nationwide household survey of residents aged > or = 16 years was carried out between 2003 and 2004. The World Mental Health Composite International Diagnostic Interview (CIDI 3.0) was used to obtain DSM-IV diagnoses. Serious mental illness (SMI) was defined as for the World Mental Health Surveys Initiative and the USA National Comorbidity Survey Replication. Participants were randomly assigned to receive the 'past month' K10 or the 'worst month in the past 12 months' K10. There were 12 992 completed interviews; 7435 included the K10. The overall response rate was 73.3%. Receiver operator characteristic (ROC) curves were used to examine the ability of both K10 versions to discriminate between CIDI 3.0 cases and non-cases, and to predict SMI., Results: Scores on both versions of the K10 were higher for female subjects, younger people, people with fewer educational qualifications, people with lower household income and people resident in more socioeconomically deprived areas. Both versions of the K10 were effective in discriminating between CIDI 3.0 cases and non-cases for anxiety disorder, mood disorders and any study disorder. The worst month in the past 12 months K10 is a more effective predictor than the past 1 month K10 of SMI (area under the curve: 0.89 vs 0.80)., Conclusions: Either version of the K10 could be used in repeated health surveys to monitor the mental health status of the New Zealand population and to derive proxy prevalence estimates for SMI. The worst month in the past 12 months K10 may be the preferred version in such surveys, because it is a better predictor of SMI than the past month K10 and also has a more logical relationship to 12 month disorder and 12 month service use.

Objective: To show the extent and patterning of 12 month mental disorder comorbidity in the New Zealand population, and its association with case severity, suicidality and health service utilization., Method: A nationwide face-to-face household survey was carried out in October 2003 to December 2004 with 12,992 participants aged 16 years and over, achieving a response rate of 73.3%. The measurement of mental disorder was with the World Mental Health Survey Initiative version of the Composite International Diagnostic Interview (CIDI 3.0). Comorbidity was analysed with hierarchy, consistent with a clinical approach to disorder count., Results: Comorbidity occurred among 37% of 12 month cases. Anxiety and mood disorders were most frequently comorbid. Strong bivariate associations occurred between alcohol and drug use disorders and, to a lesser extent, between substance use disorders and some anxiety and mood disorders. Comorbidity was associated with case severity, with suicidal behaviour (especially suicide attempts) and with health sector use (especially mental health service use)., Conclusion: The widespread nature of mental disorder comorbidity has implications for the configuration of mental health services and for clinical practice.

Objective: To estimate the prevalence of chronic physical conditions, and the risk factors for those conditions, among those with 12 month mental disorder; to estimate the prevalence of 12 month mental disorder among those with chronic physical conditions., Method: A nationally representative face-to-face household survey was carried out in October 2003 to December 2004 with 12,992 participants aged 16 years and over, achieving a response rate of 73.3%. Mental disorders were measured with the World Mental Health version of the Composite International Diagnostic Interview (CIDI 3.0). Physical conditions were self-reported. All associations are reported adjusted for age and sex., Results: People with (any) mental disorder, relative to those without mental disorder, had higher prevalences of several chronic physical conditions (chronic pain, cardiovascular disease, high blood pressure and respiratory conditions) and chronic condition risk factors (smoking, overweight/obesity, hazardous alcohol use). Around a quarter of people with chronic physical conditions had a comorbid mental disorder compared with 15% of the population without chronic conditions. Significant relationships occurred between some mental disorders and obesity, cardiovascular disease and diabetes for females, but not for males., Conclusions: This paper provides evidence of substantial comorbidity between mental disorders and chronic physical conditions in New Zealand. This should be borne in mind by clinicians working in both mental health and medical services.

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.

Objective: To estimate the prevalence and severity of anxiety, mood, substance and eating disorders in New Zealand, and associated disability and treatment., Method: A nationwide face-to-face household survey of residents aged 16 years and over was undertaken between 2003 and 2004. Lay interviewers administered a computerized fully structured diagnostic interview, the World Health Organization World Mental Health Survey Initiative version of the Composite International Diagnostic Interview. Oversampling doubled the number of Māori and quadrupled the number of Pacific people. The outcomes reported are demographics, period prevalences, 12 month severity and correlates of disorder, and contact with the health sector, within the past 12 months., Results: The response rate was 73.3%. There were 12,992 participants (2,595 Māori and 2,236 Pacific people). Period prevalences were as follows: 39.5% had met criteria for a DSM-IV mental disorder at any time in their life before interview, 20.7% had experienced disorder within the past 12 months and 11.6% within the past month. In the past 12 months, 4.7% of the population experienced serious disorder, 9.4% moderate disorder and 6.6% mild disorder. A visit for mental health problems was made to the health-care sector in the past 12 months by 58.0% of those with serious disorder, 36.5% with moderate disorder, 18.5% with mild disorder and 5.7% of those not diagnosed with a disorder. The prevalence of disorder and of serious disorder was higher for younger people and people with less education or lower household income. In contrast, these correlates had little relationship to treatment contact, after adjustment for severity. Compared with the composite Others group, Māori and Pacific people had higher prevalences of disorder, unadjusted for sociodemographic correlates, and were less likely to make treatment contact, in relation to need., Conclusions: Mental disorder is common in New Zealand. Many people with current disorder are not receiving treatment, even among those with serious disorder.

Objective: To show the disability associated with 1 month mental disorders and chronic physical conditions for the New Zealand population, controlling for comorbidity, age and sex., Method: A nationally representative face-to-face household survey was carried out from October 2003 to December 2004 with 12,992 participants aged 16 years and over, achieving a response rate of 73.3%. Mental disorders were measured with the World Mental Health (WMH) Survey Initiative version of the Composite International Diagnostic Interview (CIDI 3.0). Disability was measured with the WMH Survey Initiative version of the World Health Organization Disability Assessment Schedule (WMH WHO-DAS) in the long-form subsample (n = 7435). Outcomes include five WMH WHO-DAS domain scores for those with 1 month mental disorders and with chronic physical conditions., Results: Mood disorders were associated with more disability than anxiety or substance use disorders. Experiencing multiple mental disorders was associated with substantial role impairment. Mental disorders and chronic physical conditions were associated with similar degrees of disability on average. The combination of mental and physical disorders had additive effects on associated disability., Conclusions: Mood disorders are disabling. The investigation of disability in relation to 1 month rather than 12 month disorders is likely to provide a clearer indication of the disability associated with mood disorders. Although some researchers have queried whether negative mood can lead to 'over-reporting' of disability, recent conceptualizations of disability provide a perspective which may ease such concerns. Comorbidity, of mental disorders or of mental and physical disorders, is disabling.

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.