Onset and lifetime use of drugs in New Zealand: results from Te Rau Hinengaro: the New Zealand Mental Health Survey 2003-2004.

Introduction And Aims: Onset and lifetime use of drugs have not previously been reported for all adult ages in New Zealand. This paper reports such results and, for people born in New Zealand, compares age of onset across ethnic groups.

Design And Methods: A nationally representative cross-sectional survey was carried out in 2003-2004, with oversampling of Māori and Pacific people. Participants were aged 16 years or more, living in permanent private dwellings. In the Composite International Diagnostic Interview (CIDI 3.0), participants were asked if they had ever used drugs (alcohol, tobacco and five groups of other drugs) and the age of first use (except for tobacco). Estimates are weighted.

Results: The response rate of 73.3% yielded 12 992 interviews. The percentage of participants who had ever used drugs was: 94.6% for alcohol, 50.8% for tobacco and 42.6% for any extramedical drug, including 41.6% for cannabis, 4.2% for cocaine and 2.9% for opioids. Use was much more common in recent cohorts for extramedical drugs. The median age of onset in each age cohort was always lowest for alcohol, then cannabis, then opioids, then cocaine. Among those born in New Zealand, Māori were more at risk of use than 'Others' with the lowest risk for Pacific people.

Discussion And Conclusions: Interventions to prevent or to delay the onset of drug use need to occur before and during adolescence. The major cohort differences and the widespread experience of cannabis use help to explain the diversity of opinion in New Zealand about how to deal with this drug.