“The general finding is that physical health tends to improve in prison and then dramatically declines after people leave prison,” Western told me. “This is mostly because they’re better able to manage chronic conditions while they’re in prison, and they’re able to stay on their meds and so on.”

Mental health is another realm altogether, and Homeward illuminates the staggering burden of mental-health and addiction issues that the violence and isolation of prison can exacerbate. “We know far less about people’s mental-health status and the management of mental illness on the inside, and certainly we heard reports of depression, PTSD, anxiety, and such on the inside,” Western told me.

As grim a picture as Homeward paints, the case study actually describes a best-case scenario in the United States: Massachusetts has a relatively robust state Medicaid program that automatically enrolls people upon reentry, and can provide low- or no-cost services, including mental-health services. But the book shows, in detail, how people leaving prison don’t often seek care before major problems manifest.

“So much happens in those first 30 days, and there’s so many other kinds of stress that they’re dealing with,” Western said. People have to adjust to the minutiae of everyday life that was previously under tight control or unavailable to them—think walking in crowds, using telephones, and taking public transit. Sudden exposure to the hustle and bustle of Boston almost seems to be a trauma unto itself for people still coping with the long-term effects of prison.

The picture Western paints is bleakest for people dealing with substance abuse. While the enforced prohibition of drugs in prisons forces sobriety on inmates, Homeward shows how difficult it can be to remain sober upon reentry. Heavy substance abuse is known for straining familial and friend networks, and imprisonment often involves the intentional severing of those networks.

Homeward chronicles the lives of several people with addictions who leave prison with threadbare social networks. Almost invariably they wind up using again, end up back in prison, or both. The point of failure is often one that many outsiders might sneer at: personal willpower. But the willpower needed to overcome addictions without social support can be easily eroded, Western argues. “Much of the agency—the will to change—that even our most humane rehabilitative programs ask of people in prison is compromised by precisely the physical and mental difficulties that places them at risk of incarceration in the first place,” Western writes. “The people we ask to make the largest changes in their lives often have the least capacity to do so.”

This seems to be true of the entire project of incarceration. Especially in the realm of physical and mental health, poor people and people of color have the least resources and the least capacity to treat illness and promote wellness. That much is known—those groups are prone to higher rates of obesity, diabetes, kidney failure, asthma, and almost every other mortality indicator, including undiagnosed or poorly managed mental-health issues. Instead of extending the safety net to deal with these factors, it’s prison time that’s extended: People with drug-use and mental-health issues are incarcerated rather than funneled toward treatment and preventative care—a punishment that worsens both physical and mental-health outcomes for them and their families.