Prisons and jails in the United States have been increasingly deadly places in recent years, according to new federal data. But one cause of death has climbed most dramatically: overdoses.

From 2001 to 2018, the number of people who have died of drug or alcohol intoxication in state prisons increased by more than 600%, according to an analysis of newly-released data from the Bureau of Justice Statistics. In county jails, overdose deaths increased by over 200%.

Most of these increases have come in recent years: 2018 brought the highest number of prison deaths on record since the federal government began collecting this data 20 years ago — and that was before the pandemic. (The new federal data does not include 2019 or 2020.)

Even outside of prisons and jails, drug overdose deaths are at historic levels, according to federal data released on Wednesday. Last year, the nationwide death toll increased by nearly 30% from 2019. The devastating trend was driven by opioids, primarily illegal fentanyl.

Behind bars, overdose deaths may have risen so sharply because drug use is not only widespread there, but also uniquely dangerous, said Harold Pollack, a University of Chicago professor who studies drug use in prison. “Substances that come into the jail or prison don’t exactly go through the FDA lab to know what’s in there,” he said.

Adding to the risk, people in prison often use drugs when they’re alone and may be reluctant to call for help if there’s a problem. Even if they do seek help, medical care is often scarce and subpar. And access to drugs is erratic, which leads to rapid changes in tolerance, putting users at higher risk for an overdose.

These numbers highlight persistent issues with the way the U.S. handles drug use: incarcerating people with substance use problems and then not providing them adequate treatment, said Wanda Bertram, spokesperson for the Prison Policy Initiative, which recently published two analyses of the new federal data. “Drug addiction is a serious illness.”

The new data does not include information about which drugs people are using behind bars. But interviews with currently and formerly incarcerated people in five states and the federal system, plus news reports and death data from the Texas, California, and Arizona corrections departments, suggest that opioids (especially fentanyl), methamphetamine, and the synthetic marijuana drug K2 are largely to blame.

In prison, “people are bored and miserable and isolated, often self-medicating for mental and physical health needs that usually go unmet,” says Leo Beletsky, a law professor at Northeastern University who studies the intersection of public health and law enforcement. “Is it surprising that there’s such a demand for drugs in detention settings? Absolutely not.”

Read the full article about the overdose crisis in prisons by Beth Schwartzapfel at The Marshall Project.