The type of care veterans receive for substance use disorders and mental illness varies around the country, according to a new study. No Veterans Affairs facilities consistently performed above or below average, the researchers found.

Only 16 percent of veterans with alcohol dependence are treated with drug therapy, while 60 percent of veterans with acute depression receive drug treatment, Medical News Today reports. Less than one-third of veterans diagnosed with schizophrenia or bipolar disorder receive continuous treatment with antipsychotic drugs or mood stabilizers, the article notes.

“There is a need for substantial improvement in the care of these veterans, particularly with respect to ensuring the delivery of evidence-based treatments,” the researchers report in the journal Health Affairs.

The study, conducted by the RAND Corporation, found the quality of care for veterans was similar to or better than the care given to comparable patients with private insurance, or those enrolled in Medicaid or Medicare.

“While the VA does a better job at providing mental health services than other health care systems, there is still substantial room for improvement,” lead researcher Dr. Katherine Watkins said in a news release. “With some changes, the VA could provide even better and more cost-effective care for the nation’s veterans, as well as serve as a model for other health care systems.”

According to RAND, the number of veterans diagnosed with mental illness and substance use disorders increased 38 percent between 2004 and 2008, to 906,394. The greatest rise was seen among veterans with post-traumatic stress disorder.

The study found treating U.S. veterans with substance use disorders and mental illness cost more than $12 billion in 2007. The average cost for treating a veteran with mental illness and substance use was $12,337, or 2.7 times the cost for an average veteran without these conditions.