Mental disorder comorbidity in Te Rau Hinengaro: the New Zealand Mental Health Survey.

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.