Sen. Ron Johnson, R-Wisconsin, led a hearing of the Senate Homeland Security and Government Affairs Committee where he explored whether Medicaid expansion is at least partially to blame for the rise in opioid addiction and overdose deaths. Federal data, however, shows those problem began more than a decade earlier.

Johnson’s argument in an op-ed for the Milwaukee Journal Sentinel mentioned the case of Ramphis Pacheco, a Connecticut man who trafficked more than $185,000 worth of oxycodone. His suppliers were Medicaid beneficiaries were paid approximately $50 to obtain the pills from their physicians.

“Beneficiaries paid nothing for the drugs, and since their prescriptions and Medicaid cards were genuine, most pharmacies weren’t suspicious,” Johnson wrote.

There have also been claims of correlation between states that expanded Medicaid and those with the highest drug overdose death rates. The theory doesn’t match the timeline, however: Trends in opioids deaths nationally and by Medicaid expansion status predate the passage of the Affordable Care Act, beginning to rise in the late 1990s. The Centers for Disease Control and Prevention (CDC) declared opioid addiction an epidemic in 2011—three years before the ACA expanded Medicaid eligibility.

Andrew Kolodny, MD, co-director of the Opioid Policy Research Collaborative at Brandeis University, told Vox before the hearing the correlation touted by Johnson is “pretty ridiculous.” In his testimony at the hearing, he said the primary driver of opioid addiction has been established as “caused by the medical community overprescribing opioids.”

This began in the 1990s, Kolodny said, because physicians began responding to more aggressive marketing of opioid painkillers and were made to believe patients were suffering “because we were too stingy with opioids.”

“I believe the access to prescribers that Medicaid, Medicare and commercial insurance offers does increase the likelihood that someone might develop a disease often caused by prescriptions,” Kolodny said in his written testimony. “But I do not believe that Medicaid should be singled out in this regard. Opioid overdoses have been increasing in people with all types of insurance and in people from all economic groups, from rich to poor.”

Johnson’s position was supported at the hearing by the Foundation for Government Accountability, a conservative think tank. Its senior fellow, Sam Adolphsen, said in his time as chief operating officer at Maine’s department of health and human services, he “regularly saw the intersection between the criminal drug world and welfare benefits, including Medicaid.” In states which expanded Medicaid, he argued, opioid-related emergency department visits have spiked since Medicaid expansion began.

“Expansion has really opened the door to a massive increase in these opioids in the market on the supply side,” Adolphsen said. “When you look at a state that has expanded, that’s added hundreds of thousands of people who suddenly are not just eligible for the treatment, but they’re also eligible for no-cost prescriptions, you’re inevitably driving up the supply of this into the market.”

Kolodny, however, said the sharp rise in opioid-related deaths is due to wider availability of more dangerous opioids on the black market, particularly fentanyl, beginning in 2013. He told members of the committee Medicaid expansion isn’t causing the opioid epidemic, but the program could be utilized to alleviate the crisis by providing more addiction treatment services.

“We must ensure that in every county in the US an opioid-addicted American can walk into an outpatient treatment center and receive effective care that same day, regardless of their ability to pay for it. Until that happens, I believe overdose deaths will remain at record high levels,” Kolodny said.