SUICIDE IN NEW-ZEALAND 1957-1986 - THE INFLUENCE OF AGE, PERIOD AND BIRTH-COHORT

New Zealand suicide rates from 1957 to 1986 were analysed for age, period and cohort effects. Cumulative suicide rates were relatively stable but more complex patterns were revealed by detailed analysis. There was a steadily increasing rate in young men and a recent increase in elderly men. Reduced mortality rates in equivalent categories of accidental and "undetermined" deaths could have accounted for only a proportion of these increases. A cohort effect was noted in men, with increasing risks of suicide in the young for successive birth-cohorts born from 1947 onwards. In women a period effect was likely, with increasing rates for all age-groups between 1957-61 and 1962-66, followed by a decline recently among all except the youngest age-groups. These trends in women may have been largely due to changes in barbiturate prescribing. In both sexes poisoning declined as a method of suicide, while hanging and carbon monoxide poisoning increased. Firearm suicides also increased in men. The implications of these results for prevention are considered.