The CCDSS identified individuals as having used health services for a mental illness if they
met the following criteria: at least one physician claim listing a mental illness diagnostic code
in the first field, or one hospital discharge abstract listing a mental illness diagnostic code
in the most responsible diagnosis field using ICD-9 or ICD-9-CM codes, or their ICD-10-CA
equivalents (Table 1). Using this “omnibus” case definition, individuals must qualify as a
case in a given fiscal year to be counted in that fiscal year; therefore, estimates represent
the annual prevalence. For information on the feasibility and validation work carried out to
expand the CCDSS to include mental illness, refer to Appendix B