There are 10 times more mentally ill Americans in prisons and jails than in state psychiatric hospitals, a report published Tuesday found — adding that those individuals’ conditions often deteriorate while they are incarcerated.

The report, “The Treatment of Persons With Mental Illness in Prisons and Jails,” called for reform of laws and practices focused on the treatment of mental illness. It also encouraged cost studies to compare the true cost of housing individuals in prisons or jails as opposed to treating them in the community.

Mentally ill Americans who are imprisoned often leave incarceration sicker than when they entered, according to the report, released by the Treatment Advocacy Center, a nonprofit organization dedicated to eliminating barriers to the timely and effective treatment of severe mental illness.

“The lack of treatment for seriously ill inmates is inhumane and should not be allowed in a civilized society,” Dr. E. Fuller Torrey, founder of the Treatment Advocacy Center and lead author of the study, said Tuesday in a statement.

In 2012, there were an estimated 356,268 inmates with severe mental illnesses in U.S. prisons and jails. There were only 35,000 mentally ill individuals in state psychiatric hospitals.

“In 44 of the 50 states and the District of Columbia, a prison or jail in that state holds more individuals with serious mental illness than the largest remaining state psychiatric hospital,” the report said. “For example, in Ohio, 10 state prisons and two county jails each hold more mentally ill inmates than does the largest remaining state hospital.”

Some mentally ill prisoners refuse treatment because they are unaware of their illness — which worsens their symptoms, the report said. Treatment for mental illness is a right affirmed by the U.S. Supreme Court.

The incarceration of these individuals leads to increased taxpayer costs in the long run, according to the report. Mentally ill prisoners have higher rates of recidivism.

The National Alliance on Mental Illness (NAMI) — the nation’s largest grassroots mental health organization — offers alternatives to incarceration on its website. NAMI suggests training programs for police officers who come into contact with people with severe mental illnesses in their communities to recognize the signs and symptoms and respond appropriately.

State courts should also be given the authority to divert nonviolent offenders with severe mental illness away from incarceration and into appropriate treatment, NAMI said.

In December, the White House announced a $100 million campaign to increase access to mental health services.

"The fact that less than half of children and adults with diagnosable mental health problems receive the treatment they need is unacceptable. The President and I have made it a priority to do everything we can to make it easier to access mental health services," Vice President Joe Biden said in a statement on Dec. 10.

Mentally ill people were routinely confined to prisons and jails until the early 19th century, when the practice was deemed inhumane and problematic, and they were hospitalized instead. But following a series of exposés on the “abysmal” conditions of those psychiatric hospitals, many were closed by the 1970s.

In prisons and jails today, mentally ill prisoners are often victimized or sent to solitary confinement, and they attempt suicide at disproportionate rates, according to the report.

The study added, “By shifting the venue of these mentally ill individuals from hospitals to prisons and jails, we have succeeded in replicating the abysmal conditions of the past but in a nonclinical setting whose fundamental purpose is not medical in nature.”