Pushing more of the cost of prescription drugs onto consumers causes patients to cut back, sometimes with adverse health consequences, according to a review of two decades worth of studies published on Tuesday.

Such devices as higher co-payments, monthly limits and benefit caps are "associated with lower rates of drug treatment, worse adherence among existing users, and more frequent discontinuation of therapy," said the report from RAND, Santa Monica, California.

"For each 10 percent increase in cost sharing, prescription drug spending decreases by 2 percent to 6 percent, depending on class of drug and condition of the patient," added the study published in the Journal of the American Medical Association.

For some chronic conditions such as congestive heart failure, high cholesterol, diabetes, schizophrenia and perhaps asthma, higher cost sharing seems to result in increased use of medical services, such as visits to emergency rooms or hospitals, the report said.

The findings were based on a review of 132 studies done on the topic between 1985 and 2006.

"These findings make benefit design an important public health tool for improving population health. The challenge for public and private plans is to make patients more sensitive to the cost of treatment without encouraging them to forego cost-effective care," the study concluded.