SACRAMENTO (AP) — A federal judge’s objection to what he called the horrific treatment of some mentally ill inmates in California prisons highlights a trend that has been building for decades in the state and across the country: As mental hospitals closed or were scaled back, prisons and county jails have become the de facto housing for many who are mentally ill.

The state is struggling to deal with more than 33,000 mentally ill inmates, accounting for more than a quarter of the population of 120,000 in California’s major prisons. By comparison, California’s five state psychiatric hospitals combined now serve fewer than 6,000 patients.

Nationwide, 10 times more seriously mentally ill individuals are in state prisons and jails than in state mental hospitals, the Arlington, Va.-based Treatment Advocacy Center and the National Sheriffs’ Association said last week in what it called the first national study of how mentally ill inmates receive treatment. It estimated there are 356,000 mentally ill inmates nationwide, compared with 35,000 patients in public mental hospitals.

“Prison and jail officials are being asked to assume responsibility for the nation’s most seriously mentally ill individuals, despite the fact that the officials did not sign up to do this job; are not trained to do it; face severe legal restrictions in their ability to provide treatment for such individuals; and yet are held responsible when things go wrong, as they inevitably do under such circumstances,” the study said.

In 44 states, including California, the largest institution housing those with severe psychiatric problems is now a prison or jail, according to the study.

In California, inadequate treatment has led to more than two decades of federal court oversight of mental health operations in prisons. More recent lawsuits allege that some California counties have similar deficiencies in their jails.

State corrections officials did not comment despite repeated requests since Friday.

U.S. District Judge Lawrence Karlton of Sacramento ruled last week that excessive use of force and isolation of mentally ill inmates continues, violating their constitutional rights against cruel and unusual punishment. In his ruling, the judge said that has led to the potential for more severe psychosis and even suicide.

“Unfortunately, in California, we have turned the prisons into mental health institutions,” Karlton said as he heard arguments in the case in December.

The veteran judge ordered the state to further restrict its use of pepper spray and prolonged solitary confinement when dealing with mentally ill inmates.

Over the last decade, the number of mentally ill inmates in California prisons nearly doubled — from about 20,000 in 2000 to a peak of about 37,000 in 2011 — before the overall prison population was dramatically reduced under a three-year-old law that keeps most of the less-serious offenders in county jails.

But the number of mentally ill inmates began climbing steadily again in mid-2012 and rose by more than 300 inmates in just three months last year, the judge noted.

“California has been on a helter-skelter schedule to close down its psychiatric beds since the 1970s,” said Carla Jacobs of Orange County, a founding board member of the Treatment Advocacy Center.

Housing and treating the growing number of mentally ill inmates has been difficult and expensive for California’s prison system, which has spent more than $2 billion on new mental health facilities while sharply increasing salaries for mental health professionals in the last decade. The state expects to spend $400 million on prison mental health services in the next fiscal year alone.

“We as a society have failed to set up appropriate outpatient mental health services so people who maybe could function in the community have not been able to,” said Michael Bien, one of the attorneys suing the state on behalf of mentally ill inmates.

The problem was aggravated when states and the federal government increased penalties for drug use, because the mentally ill are more likely to “self-medicate” if they don’t receive proper care, Bien said.

His San Francisco-based law firm is suing Monterey County, alleging that the county jail offers inadequate facilities and programs for inmates who are mentally ill or have other disabilities. It also sued Sutter County over the deaths of two jail inmates, one of whom committed suicide.

The seriously mentally ill often are less able to follow rules in prison, making it more likely they will be pepper sprayed or placed in solitary confinement, the problems the federal judge addressed in his ruling.

“All these things make people with mental illness get sicker,” Bien said. “So we have a vicious cycle.”