Mental health emergency department visits: An exploration of case definitions in North Carolina

Mental health (MH) disorders comprise a high disease burden and have long-lasting impacts. To improve MH, it is important to define public health MH surveillance. We compared MH related definitions using ICD-10-CM codes: The Council of State and Territorial Epidemiologists' (CSTE) surveillance indicators for all MH, mood or depressive, schizophrenic, and drug/alcohol-induced disorders; and North Carolina's (NC) syndromic surveillance system's definition for anxiety/mood/psychotic disorders, and suicide/self-harm. We compared code definitions and frequent codes in 2019 emergency department (ED) data for those age ≥ 10 years. CSTE's definition resulted in over one million MH-related visits (23% of all ED visits) and NC's definitions in 451,807 MH-related visits (9% of all ED visits). Using CSTE's broadest definition, nicotine use was the most common visit type; using NC's definitions, it was major depressive disorder. Standardizing population-level MH indicators benefits surveillance efforts. Given its prevalence, efforts should focus on documenting MH to improve treatment and prevention. •There are large discrepancies in Mental Health visit prevalence by definition.•Broad Mental Health definitions also capture Substance Use.•Excluding Substance Use, major depressive disorder is the most common code.•Standardizing Mental Health indicators is important for surveillance efforts.