Attorney General Jeff Sessions jump-started the war on drugs in a recent memo to federal prosecutors, ordering them to “charge and pursue” the toughest penalties possible, even for low-level offenses.

The new policy is expected to increase the prison population and punish minority groups, particularly African Americans, that have been disproportionately subjected to mandatory minimums for minor drug crimes.

But there’s a looming, and less obvious, side effect of this new directive: The White House’s “tough on crime” approach is almost certainly going to exacerbate the spread of infectious diseases like HIV.

In a new systematic review of 106 studies on criminalization and HIV, published this week in The Lancet HIV, researchers found the vast majority of studies (more than 80 percent) show criminalization is associated with harmful effects for those targeted by the laws as well as their communities: increasing drug use, increasing the use of shared needles for drug injections, and driving up HIV infections, among other troubling effects.

This disconnect between the evidence and the White House’s new policy has shocked the public health community, said Stefan Baral, one of the study authors and an associate professor of epidemiology at the Bloomberg School of Public Health. “The evidence is overwhelming,” he added. “The Sessions memo is just incredibly sad.”

A “tough on crime” approach can exacerbate HIV among injection drug users

During the Obama era, former Attorney General Eric Holder advised federal prosecutors to do the opposite of what Sessions is suggesting now — and avoid mandatory minimums for low-level, nonviolent drug offenses.

Between 2008 and 2013, HIV rates declined in the US, in part because of a drop-off among injection drug users.

One big reason why, Baral explained: Criminalization drives injection drug users underground, making them more likely to share needles — and helping diseases like HIV spread more rapidly among users.

“Almost invariably, when you increase policing, people are more hidden in terms of how they are injecting,” said Baral. On the other hand, he added, “It’s a global truth that when someone who is using drugs has access to a clean needle — they will use it.”

That’s exactly what happened in rural Indiana when Vice President Mike Pence was the governor. He first resisted pleas from public health officials for the state to provide clean needles during an out-of-control 2015 HIV outbreak among injection drug users. (The evidence suggests clean needle exchanges reduce the rate of HIV transmission among drug users.) More than two months into the outbreak, Pence changed his mind. The HIV rate in Indiana dropped precipitously — and the needle exchange is seen as the major reason for the turnaround.

Mass incarceration is a significant driver of STDs

Policies that lead to mass incarceration contribute to infectious disease spread in other ways: When you have people coming in and out of prison, people’s sexual patterns are disrupted, Duke researcher Susan Reif told me. Prisons have higher rates of STDs, and when prisoners return to the community, they may bring with them any diseases they picked up while incarcerated — not just HIV. “Incarceration is a significant driver of HIV and STDs," Reif summed up.

The Obama-era efforts to reduce mandatory minimums enjoyed broad bipartisan support. And that’s part of the reason why the new push to undo that work has garnered criticism from both sides of the aisle. As Eric Holder said of the new policy, “[It’s] not tough on crime. It is dumb on crime.”

Republicans such as Rand Paul have also been speaking out against Sessions’s backward approach. “We should be treating our nation's drug epidemic for what it is — a public health crisis,” he wrote in a CNN op-ed.

Instead of throwing drug users in prison, Baral, the epidemiologist, would like to see the White House enact policies based on evidence — creating programs for safe needle exchanges, for example, and expanding treatment options for addicts.

“We are at a watershed moment turning back these improvements,” he added. “[The Sessions memo] is a clear move back to putting more and more and more people in jail, which is just something that will a) drive more people underground, [and] b) have no positive health consequences for anybody.”