CHICAGO (Reuters) - Many more Americans have been using prescription drugs to treat mental illness since 1996, in part because of expanded insurance coverage and greater familiarity with the drugs among primary care doctors, U.S. researchers said on Tuesday.

They said 73 percent more adults and 50 percent more children are using drugs to treat mental illness than in 1996.

Among adults over 65, use of so-called psychotropic drugs - which include antidepressants, antipsychotics and
Alzheimer's medicines - doubled between 1996 and 2006.

"What we generally find is there has been an increase in access to care for all populations," said Sherry Glied of
Columbia University in New York, whose study appears in the journal Health Affairs.

"Mental health has become much more a part of mainstream medical care," Glied said in a telephone interview.

In 2006, they said 16 percent of adults 65 and older had some form of mental health diagnosis.

The researchers culled data from several large public surveys of health in the United States, including from the
National Center for Health Statistics, the Agency for Healthcare Research and Quality, the Substance Abuse and Mental Health Services Administration and the Social Security Administration.

Glied said expanded drug coverage under Medicare, the federal insurance program for the elderly, and the State
Children's Health Insurance Program for poor children, helped make such drugs more affordable.

The study found the number of children diagnosed and treated for mental health conditions by their primary care
doctor doubled between 1996 and 2006.

"The increases in prescription drug use were particularly rapid in the early part of this decade, between 1996 to 2001," Glied said. "For most groups, they have slowed down since then."

The researchers did not report total numbers of people treated or calculate the dollar value of the drugs taken.

One worrisome finding, Glied said, was that there has been little progress in access to care among people with more
serious mental illness.

They found treatment for older adults with mental limitations who need help dressing, eating, or bathing fell between 1996 and 2006.

About 7 percent of Americans with serious mental illness wind up in jail or prison every year, the researchers said.

"New policies are desperately needed to reduce the flow of people whose primary problem is a mental disorder into the criminal justice system," wrote Glied and colleague Richard Frank of Harvard Medical School.

While the study shows expanded mental health coverage for people with insurance, especially for those covered in
government health plans, they said the ongoing recession and swelling ranks of the uninsured will likely mean less mental health coverage for many Americans in the near future.