When Ashley Hurteau, 32, was arrested in 2015, she faced a list of charges for crimes she committed to finance a drug craving she had struggled with for more than a decade.

“I wasn’t using it to get high,” she said. “I was using it to survive.”

Homeless, uninsured and addicted to heroin, Hurteau, a New Hampshire resident, had tried and failed to get help. Services came at a price she couldn’t afford.

But in 2014, Hurteau’s home state of New Hampshire expanded Medicaid. She qualified for coverage, giving her access to intensive outpatient treatment through the county’s drug court program.

New Hampshire, along with 30 other states and the District of Columbia, expanded eligibility for the state-federal low-income health insurance program under the Affordable Care Act. Hurteau is among the 1.6 million Americans who since then have had access to substance abuse services.

But a study published Monday in the journal Health Affairs found significant disparities in coverage among the states.

Researchers sought to determine the number of substance treatment services available in each state in 2014. They analyzed coverage for the four tiers of services recognized by the American Society for Addiction Medicine, which are classified as outpatient (including group and individual therapy as well as recovery support services), intensive outpatient, short- and long-term residential inpatient and intensive inpatient care for detoxification. Data was collected from the annual National Drug Abuse Treatment System Survey and state Medicaid directors.

At the time of the study, 21 states had expanded Medicaid. The federal health law required states that chose to expand their Medicaid programs to include coverage for substance abuse treatment. But it gave states control to decide the type of treatment and medication that would be covered.

Overall, the researchers found the level of Medicaid coverage for substance abuse treatment did not correlate with Medicaid expansion. Thirteen states and the District of Columbia insured each of the services in all tiers, and 26 states covered at least one service in each level of treatment.

Nine states did not provide Medicaid reimbursement for any substance abuse care in at least two levels of treatment. In particular, states shied away from covering residential interventions, which the federal government had historically chosen not to reimburse for mentally ill patients insured by Medicaid.

The expansion has forged a path for thousands to access substance abuse services. In Rhode Island, over 3,600 individuals obtained treatment through the additional coverage. From January 2015 to March 2016, nearly 63,000 people in Massachusetts received services.

Colleen Grogan, a professor at the University of Chicago and lead author of the study, said that although gaps in coverage remain, undoing the Medicaid expansion as part of the current push by Republican lawmakers and President-elect Donald Trump could have serious consequences for the nation’s efforts to address the ongoing opioid epidemic.

“If we repeal the ACA, I think that’s going to make it worse,” she said.

Deaths by overdose have quadrupled since 2000, totaling more than 28,600 fatalities in 2014, according to the Centers for Disease Control and Prevention. In North Dakota alone, the number of cases surged by 125 percent in one year. In New Hampshire, the rate rose by nearly 75 percent.

Grogan said the variety of coverage across the nation also didn’t align along political lines, pointing to the severity of substance abuse across the nation and states’ commitment to address the issue.

“It’s really hard to address the epidemic if you can’t get people connected to services,” she said.

The coverage disparity across the nation extended to medications used to manage addiction. Every state and the District of Columbia insured buprenorphine, and all but two states covered injectable naltrexone. However, only 32 Medicaid programs covered methadone, one of the most effective drugs in managing addiction, according to the American Society for Addiction Medicine.

Only 17 state programs and the District of Columbia insured both comprehensive treatment services and all addiction medications.

The large number of states paying for these drugs surprised Grogan, she said. Although relatively low rates of methadone coverage reveal residual stigma toward the medication, the overall rise in drug coverage indicates a national shift in accepting drugs as a viable treatment option for recovering addicts rather than “replacing one addiction with another.”

“We’ve moved quite a ways in accepting that medication for the rest of your life is needed,” Grogan said.

But the study also revealed several hurdles in accessing services and life-saving medication. It found many states limited access to substance abuse treatment by requiring preauthorization, imposing annual maximums or asking for patients to pay a share of the costs.

Nearly every state required preauthorization and over a third of them required copays for buprenorphine. About half the states imposed preauthorization for intensive inpatient facilities. Nearly 10 states extended the annual maximums to recovery services.

“When you have a patient that is ready to get treatment that is in withdrawal, that is the moment where you really need as few barriers as possible,” said Yngvild Olsen, chair of the public policy committee for the American Society of Addiction Medicine.

When Hurteau entered treatment, New Hampshire was streamlining the process to allow patients to access care with few hurdles. Although the study says the state is missing intensive outpatient residential treatment programs, the state expanded Medicaid under a waiver and provides comprehensive services through a substance use disorder benefits package.

Michele Merritt, policy director at New Futures, a nonprofit organization that works to address substance abuse issues in New Hampshire, said expanding Medicaid enabled the state to connect 10,000 people to treatment in 2015, she said. Prior to that, the state relied solely on grants to support their system, she said, resulting in long wait lines.

“Medicaid expansion at least in my opinion is the single most important thing New Hampshire has done to combat the opioid epidemic,” Merritt said.

The possible repeal of the ACA raises serious concerns for Grogan, Merritt and Olsen. All three women touted the importance of comprehensive services, rather than piecemeal interventions, as key to tackling the epidemic. These services cost money, Grogan admitted, but the fiscal and societal costs of neglecting the opioid epidemic outweigh the initial investment.

“I think even from a moral perspective, we know that we need to respond to people who have addiction,” Grogan said. “Especially for those that have reached a point that want help.”

Hurteau’s life has dramatically changed.

Today, Hurteau works as a volunteer and program coordinator at Safe Harbor Recovery Center. She is able to see her son, now 3, and is on track to regain custody. A recovery support group also helps her live a life of sobriety.

“I don’t know where I would be if this wasn’t available to me,” she said.