Forty-one state attorneys general have launched investigations into the role of drug manufacturers and distributors in the opioid abuse epidemic. But perhaps they should be looking at the part Medicaid expansion may have played in producing this crisis.

Overdose deaths have increased twice as much in states that expanded Medicaid under the Affordable Care Act, according to data from the Centers for Disease Control and Prevention. Hospital and emergency room visits have also increased in states that expanded Medicaid.

Wall Street Journal editorial writer Allysia Finley explores the possible connections:

Medicaid patients may be more likely to be prescribed opioids—twice as likely, according to two studies, as privately insured individuals. A recent study by Express Scripts Holding found that about a quarter of Medicaid patients were prescribed an opioid in 2015.

State Medicaid programs also favor generics over more expensive branded painkillers with abuse-deterrent formulas. According to the Express Scripts study, generics accounted for 90% of Medicaid opioid medication claims. Large doses of oxycodone, methadone and fentanyl can be obtained cheaply with a Medicaid card and resold for a nice profit on the black market. Sen. Johnson’s review of recent open-source court files and news articles turned up 261 defendants who had been convicted of improperly using Medicaid cards to obtain prescription opioids.

Many states in recent years have set up databases to identify patients at risk for abuse based on the number of prescriptions they fill and pharmacies they visit. But often providers, particularly in emergency rooms where many Medicaid patients seek treatment, don’t have time to check the databases, examine patients for abuse, perform follow-up consultations, or consider alternative analgesics or physical therapy.

These problems have become even more acute following the expansion. Many primary-care providers won’t see Medicaid patients because of the low reimbursement rates, so emergency rooms have been inundated with patients. The wait to see a specialist can last months. Many Medicaid beneficiaries suffering from pain or substance abuse may not be getting the treatment they need.

ObamaCare defenders claim scaling back Medicaid would harm patients who suffer from substance abuse. But data on opioid overdoses and hospital admissions suggests state Medicaid programs aren’t providing effective treatment. Perhaps a rollback is what the doctor ordered.

If Medicaid expansion turns out to be a key factor in rising opioid abuse, it will be the latest example of government policy inadvertently harming people under the guise of offering help.