A Wall Street Journal editorial, “Medicaid’s Opioid Fix,” on Wednesday explains how Senator Ron Johnson, R-WI, uncovered a connection between the ObamaCare Medicaid expansion and opioid addiction:

A recent study by Express Scripts Holding found that about a quarter of Medicaid patients were prescribed an opioid in 2015. Wisconsin Sen. Ron Johnson presents intriguing evidence that the Medicaid expansion under ObamaCare may be contributing to the rise in opioid abuse. According to a federal Health and Human Services analysis requested by the Senator, overdose deaths per million residents rose twice as fast in the 29 Medicaid expansion states—those that increased eligibility to 138% from 100% of the poverty line—than in the 21 non-expansion states between 2013 and 2015.

There were also marked disparities between neighboring states based on whether they opted into ObamaCare’s Medicaid expansion. Deaths increased twice as much in New Hampshire (108%) and Maryland (44%)—expansion states—than in Maine (55%) and Virginia (22%). Drug fatalities shot up by 41% in Ohio while climbing 3% in non-expansion Wisconsin.

Using open source court files and news stories, Mr. Johnson’s office also found 261 cases of people who were recently prosecuted for exploiting Medicaid cards to obtain opioids. Last month an Army veteran was convicted of selling oxycodone pills with forged prescriptions. His co-conspirator paid for the pills with a Medicaid card.

A police detective in Wisconsin told Mr. Johnson’s office that 240 oxycodone pills can be purchased with a Medicaid card for a $1 co-pay and resold for $4,000 on the street. A single Vicodin pill can fetch $50.

In a letter to the Inspector General for the Department of Health and Human Services, Mr. Johnson last month observed that “it appears that the program has created a perverse incentive for people to use opioids, sell them for large profits and stay hooked.” He’s asked the Inspector General to investigate Medicaid’s controls to prevent such abuses.