And although it has long been suspected that prison aggravates pre-existing psychiatric problems, experts have had trouble untangling this chicken-and-egg question, especially given that early childhood experiences are linked to both incarceration and mental illness.
For the study, Schnittker and his co-authors looked at a national database of nearly 5,700 men and women to assess both the prevalence of psychiatric disorders and any time spent in jail or prison.
Their conclusion? Incarceration was associated with a 45 percent increase in the risk of having depression.
The findings did have some limitations, namely that the authors couldn't control for all other factors that might affect the incidence of depression. And because it's so difficult to conduct studies in prison populations, it's possible that the data did not pick up on worsening of conditions other than depression, said Eth, who was not involved with the study.
The data were also at least a decade old, Eth said, even though "it's likely that if the study were to be repeated now there would be similar findings."
Although the study authors advocate for more treatment while people are in prison and before being let out onto the streets, in reality conditions in correctional facilities are often pitiful, said Eth, echoing King's sentiments.
"There's very, very little treatment available to people who are in jails and prisons. At most, it's medication, and for many conditions it's nothing at all. It's terrible," Eth said. "If you didn't have a serious mental illness going in, the conditions of jails and prisons are so deplorable, you'd have to be a hardy soul not to be depressed or worse."
Unfortunately, psychiatric treatment for ex-offenders "on the outside" is also limited, said JoAnne Page, president and CEO of the Fortune Society in New York City, whic
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