State parity laws and access to treatment for substance use disorder in the United States: implications for federal parity legislation

Abstract

Importance: The passage of the 2008 Mental Health Parity and Addiction Equity Act and the 2010 Affordable Care Act incorporated parity for substance use disorder (SUD) treatment into federal legislation. However, prior research provides us with scant evidence as to whether federal parity legislation will hold the potential for improving access to SUD treatment.

Objective: To examine the effect of state-level SUD parity laws on state-aggregate SUD treatment rates and to shed light on the impact of the recent federal SUD parity legislation.

Design, setting, and participants: We conducted a quasi-experimental study using a 2-way (state and year) fixed-effect method. We included all known specialty SUD treatment facilities in the United States and examined treatment rates from October 1, 2000, through March 31, 2008. Our main source of data was the National Survey of Substance Abuse Treatment Services, which provides facility-level information on specialty SUD treatment.

Interventions: State-level SUD parity laws during the study period.

Main outcomes and measures: State-aggregate SUD treatment rates in (1) all specialty SUD treatment facilities and (2) specialty SUD treatment facilities accepting private insurance.

Results: The implementation of any SUD parity law increased the treatment rate by 9% (P < .001) in all specialty SUD treatment facilities and by 15% (P = .02) in facilities accepting private insurance. Full parity and parity only if SUD coverage is offered increased the SUD treatment rate by 13% (P = .02) and 8% (P = .04), respectively, in all facilities and by 21% (P = .03) and 10% (P = .04), respectively, in facilities accepting private insurance.

Conclusions and relevance: We found a positive effect of the implementation of state SUD parity legislation on access to specialty SUD treatment. Furthermore, the positive association is more pronounced in states with more comprehensive parity laws. Our findings suggest that federal parity legislation holds the potential to improve access to SUD treatment.

Figure 1

Trend in substance use disorder (SUD) treatment rate by SUD parity status. Note: Figure 1 presents state-aggregate SUD treatment rate during the pre- and post-parity period. We centered the year each parity state started to implement the law at Time 0. The vertical line represents the year during which each parity state started to implement or extend the law, and it corresponds to the period covered in: N-SSATS 2002 (April, 2001 to March, 2002) for DE and MI, N-SSATS 2003 (April, 2002 to March, 2003) for MT and RI, N-SSATS 2004 (April, 2003 to March, 2004) for ME and NH, N-SSATS 2005 (April, 2004 to March, 2005) for WI and WV, and N-SSATS 2007 (April, 2006 to March, 2007) 2007 for OR. Note that KY implemented parity during the gap year between N-SSATS 2000 and N-SSATS 2002, so Time 0 consisted of nine data points instead of ten. For the other “no change in parity” states, the treatment rates during 2002, 2003, 2004, 2005 and 2007 were weighted by 2/9, 2/9, 2/9, 2/9, and 1/9 to match the proportions of the states that implemented parity in a given year. Following the same procedure we determined Time −2, −1, 1, 2, and 3 for parity states, and then transferred “no change in parity” states to the corresponding time in accord with the parity states. Note that only 7 parity states were included for Time −1 (No data for KY, DE and MI), time 2 (No data for OR), and time 3 (No data for OR).