Medicaid pays for more adult mental health hospital stays than any other payer, in the 43 states that report

Significant findings

HCUP publishes hospital stays by expected payer at the state level, for the states that participate in a given year. For 2023, 43 states reported adult (age 19 and older) stays with a mental health or substance use principal diagnosis. Summing the file's quarterly counts across those states gives 1,300,400 stays for all expected payers. Of these, 486,750 were Medicaid, ages 19 to 64 (37.4 percent); 310,650 private insurance, ages 19 to 64 (23.9 percent); 148,600 Medicare, age 65 and older (11.4 percent); and 105,300 self-pay or no charge, ages 19 to 64 (8.1 percent). The file's own combined line for Medicaid plus self-pay is 592,050, or 45.5 percent.

Those four displayed categories account for 1,051,300 stays, about 81 percent of the total; the remainder are payer and age combinations the file does not display separately, such as Medicare under 65 or private insurance over 65. The file marks the total with a caret and the note that "the sum across the displayed expected payers" need not equal it.

The file also documents that its own definition of a mental health or substance use stay changed at the switch to ICD-10 coding, and publishes the size of the break for each payer, so counts before and after late 2015 are not one series.

Worth asking

This is not a national number and the API that serves the explorer refuses to pretend it is. It is the sum over the states that report, and the share of stays that Medicaid carries is the one that tells you who the mental health inpatient system is actually built for.