(Reuters Health) – Every year, an estimated 2 million people diagnosed with mental illness are jailed in the U.S., and soon after they’re released, many wind up behind bars again.

But specialized supervision on probation for people with mental illness can radically reduce the odds they’ll be re-arrested within five years, a new study suggests.

Those who were supervised on specialty probation were nearly three times less likely to return to jail within two years after their release than those on regular probation, researchers reported in JAMA Psychiatry.

Positive support appears to be key, with specialty probation officers acting as part counselor and part cop, said lead author Jennifer Skeem, professor of social welfare and public policy at the University of California at Berkeley.

“It’s about good, caring relationships with a professional. They seem to have that with specialty officers,” she said in a phone interview.

“The rules are clear. There’s fairness, there’s firmness in implementing the rules and then caring. It helps keep people out of trouble with the law,” she said.

Under specialty mental health probation, officers have smaller caseloads and training in mental illness. They coordinate probationers’ treatment and collaborate with treatment providers to keep them out of jail.

Skeem, a clinical psychologist, and her team analyzed data for ethnically diverse men and women from two urban probation agencies, one in Texas using specialty probation, and another in California employing traditional probation. All 359 participants had been diagnosed with mental illness following a psychological evaluation.

The average caseload for specialty probation officers was 50, compared to 100 probationers for traditional officers.

The odds of probationers being arrested after two years were 2.68 times higher for those on traditional probation than for those on specialty probation.

After five years, the probability of re-arrest was 64 percent for traditional probationers, compared to 38 percent for specialty probationers.

Dr. Fred Osher, director of health systems and services policy at The Council of State Governments Justice Center in New York City, called specialty mental health probation “a win-win-win.”

“They’re in the community, they’re getting the support they need, and they’re able to move forward with their own recovery,” he said in a phone interview.

“It’s hard to recover from mental illness if you’re sitting in a jail cell,” said Osher, who was not involved with the study.

The upfront costs for specialty probation are higher, but Skeem said a cost analysis she prepared as part of an as-yet unpublished follow-up study shows that specialty mental health probation saves money over the course of two years. The savings come from the reduced need for emergency room visits and other hospital stays, she said.

The study findings were consistent with less-rigorous studies pointing in the same direction, Osher said.

“It’s research like this that will allow policymakers to consider implementing a program that will have a major impact on people with mental illness in their jails,” he said.

“Even a day or two in jail really messes up a person’s life. You can end up losing your job and housing,” he said. “We want to maximize the use of alternatives to jail if individuals don’t pose a risk.”