The Effects of Changes in the World Health Organization's International Classification of Diseases on Suicide Rates in 71 Countries, 1950–1999

The World Health Organization (WHO) provides annual mortality statistics from 1950 onward based on the International Classification of Diseases (ICD). In this paper we evaluate the effects of ICD form revisions on suicide rates for 71 countries. The changes between ICD-6, ICD-7, ICD-8, and ICD-9 did not have an overall effect on reported suicide rates. The transitions to ICD-8 and ICD-9 were, however, associated with country-specific changes in the suicide rate in some countries. The change from ICD-9 to ICD-10 was associated with an overall change of -.73 suicides per 100,000 inhabitants. It is recommended that researchers using the WHO mortality data for longitudinal cross-national studies control for the ICD form used at different time points.