EXHIBIT 4.

Adjusted rates of medications for opioid use disorder for individuals in the US referred to treatment in Medicaid expansion and nonexpansion states, by treatment referral source, 2008–17

	(1) Pre-ACAa		(2) Post-ACAa		Difference (2–1)a		DIDa
	Expansion	Nonexpansion	Expansion	Nonexpansion	Expansion	Nonexpansion
CRIMINAL JUSTICE REFERRALS
All	5.5	4.2	14.5	4.6	9.0	0.4	8.6***
Race/ethnicity
Non-Hispanic White	5.0	4.2	15.0	4.3	10.0	0.1	9.8***
Non-Hispanic Black	6.7	3.9	12.7	3.4	6.0	−0.5	6.5**
Hispanic	5.6	2.6	13.6	5.2	8.0	2.6	5.4
Native American/Alaska Native	5.7	4.2	12.3	4.9	6.6	0.7	5.9***
Other race	7.8	5.8	16.5	5.3	8.6	−0.5	9.1
Service setting
Ambulatory	6.4	5.0	16.0	5.2	9.7	0.2	9.5***
Residential	3.2	1.6	10.4	2.9	7.2	1.3	5.9
OTHER REFERRALS
All	39.5	29.7	53.1	26.8	13.6	−2.9	16.5***
Race/ethnicity
Non-Hispanic White	35.5	26.0	50.8	24.6	15.4	−1.4	16.8***
Non-Hispanic Black	46.1	31.7	59.5	27.9	13.4	−3.7	17.1****
Hispanic	47.2	38.7	52.9	26.8	5.7	−11.9	17.6**
Native American/Alaskan Native	39.4	31.3	51.3	25.0	12.0	−6.3	18.2**
Other race	51.8	45.6	62.3	28.6	10.4	−17.0	27.5**
Service setting
Ambulatory	50.5	38.0	63.5	33.9	13.0	−4.1	17.1***
Residential	6.7	4.4	20.6	6.5	14.0	2.1	11.8**

SOURCE Authors’ analysis of information for 2008–17 from the Treatment Episode Data Set–Admissions, Substance Abuse and Mental Health Services Administration, linked to data on years of adoption of the Medicaid expansion. NOTES For all states, “pre-ACA” is 2008–13. For nonexpansion states, “post-ACA” is 2015–17. For expansion states, the post-ACA period begins the year after Medicaid expansion was adopted by the individual state, which was 2015 for most expansion states. ACA is Affordable Care Act. DID is difference-in-differences estimate.

^aPercentage points.

^**p < 0:05

^***p < 0:01

^****p < 0:001