Readmission rate equals the number of mental health or addiction episodes of care (EOCs) that are followed by a mental health or addiction readmission within 30 days of discharge divided by the number of mental health or addiction EOCs during the study period.

Ontario Mental Health Reporting System (OMHRS) and Discharge Abstract Database (DAD) databases are used to identify index as well as subsequent hospitalizations for mental health and addictions.

For each unique mental health or addiction EOC in the study period (denominator), calculate the number that are followed (within 30 days) by a mental health or addiction admission (numerator), defined as:

Mental Health or Addiction:
1. DAD ICD-10-CA Dx10Code1: F04 to F99,
2. OMHRS DSM-IV or DSM-V codes: Any hospital admission (including missing diagnosis except for DSM-IV 290.x. 294.x)

Deliberate Self-Harm:

3. ICD-10-CA Dx10Code1 is not equal to F04 to F99 and DXcodes2-25=X60-X84 or Y10-Y19 (Dxtype=9).

Exclusions:

• Patients without a valid health insurance number
• Patients without an Ontario residence
• Gender not recorded as male or female
• Age > 105 years
• Invalid date of birth, admission date/time, discharge date/time
• Individuals who die within 30 days of discharge (based on RPDB) before a follow-up or outcome occurs (i.e. a person dies before they have been readmitted
• Hospital admission for conditions other than mental health, addiction, or deliberate self-harm

Notes:

• Admissions for acute care for the treatment of deliberate self-harm are considered mental health admissions.
• Episodes of care (EOC) included in the denominator are restricted to calendar years but 30-day follow-up for readmission can cross over into the next calendar year.
• The reason for the readmission can be for a different MHA condition than the index discharge.

Inclusions:

• 0 - 105 years, inclusive

Exclusions:

• Patients without a valid health insurance number
• Patients without an Ontario residence
• Gender not recorded as male or female
• Age > 105 years
• Invalid date of birth, admission date/time, discharge date/time