Birth cohort effects in New South Wales suicide, 1865-1998

Objective: To examine birth cohort effects in New South Wales (NSW) suicide data (1865-1998). Method: Aggregate suicide data were examined after controlling for age and period using descriptive statistics and Poisson regression modelling. Three approaches were applied to address the non-identification of age, period and cohort in age-period-cohort (APC) models of suicide. Results: Apparent cohort effects in male and female suicide using a minimum constraints APC model of age, period and cohort were no longer present in female suicide when a surrogate period APC model was used, and were absent in both male and female suicide when identifiable cohort effects were isolated using a 'drift' adjusted approach to APC modelling. Conclusion: Increases in youth suicide rates in NSW occurring since the 1960s cannot be attributed to cohort effects, such as family influences on development. The causes of youth suicide are thus effects operating contemporaneously.