Clustering of Attempted Suicide: New Zealand National Data

BACKGROUND: The extent to which clusters of attempted suicides occur is a significant problem that is complementary to the current available research on the clustering of completed suicide. However, little systematic research on clusters of attempted suicides exists. The present study examines the extent and nature of clustering of suicide attempts. METHOD: The occurrence of clustering of attempted suicide was examined in nationwide data for all New Zealand hospitals, obtained from the New Zealand Health Statistics Services for the years 1988-1990. The Scan statistic and Knox procedure were employed for testing the significance of clusters in time and time-space, respectively. RESULTS: The analyses indicated that significant time clustering occurred in younger age groups, specifically among 15-19 and 20-24 year olds. The results could not be accounted for by seasonal variations in admissions. Age specificity of time-space clusters emerged, exhibiting a similar pattern to that reported for completed suicides in the US. CONCLUSIONS: The results suggest a similar underlying mechanism for the clustering of parasuicide and completed suicides and provide support for the existence of contagion of suicidal behaviour. The implications for prevention are discussed.