Prescription drug use is on the rise in U.S.

More Americans than ever are taking prescription drugs and they're using more of them, a new study finds.

Fifty-nine percent of adults used prescription drugs in 2011-2012, up from 51 percent in 1999-2000. And 15 percent of them took five or more prescription drugs, an increase from 8 percent in the earlier period, the researchers reported.

Cholesterol-lowering drugs (statins), antidepressants and high blood pressure medications saw especially notable jumps in usage, the study found.

"We wanted to create a comprehensive resource on prescription drug use among U.S. adults, and I think that the implications of these trends vary across classes of drugs," said lead researcher Elizabeth Kantor, who was with the Harvard School of Public Health in Boston at the time of the study.

Kantor said an increase in one drug class may mean more people are getting treated for a given condition or may reflect a change in the nation's underlying health needs.

Dr. David Katz, director of the Yale University Prevention Research Center, said the upside to increasing use of modern medications is a decline in the U.S. death rate. Modern medicines are often effective in treating disease and preventing premature death, he said.

"But, of course, not dying isn't the same as truly living, and that leads to the very ominous implications of this trend," said Katz, who is also president of the American College of Lifestyle Medicine.

Many drugs are being used to treat avoidable conditions, Katz said.

For the study, published Nov. 3 in the Journal of the American Medical Association, Kantor and her colleagues used data from the National Health and Nutrition Examination Survey to determine trends in prescription drug use among nearly 38,000 adults aged 20 and older between 1999-2000 and 2011-2012. Participants were asked about their prescription drug use in the previous 30 days.

By 2011-2012, the researchers found that:

-Twenty-seven percent of adults were taking high blood pressure drugs, up from 20 percent a decade earlier.

-Statin use more than doubled -- from seven percent to 17 percent. The overall prescription drug leader was simvastatin (Zocor), taken by nearly eight percent of adults. Just two percent took it in 1999-2000.

-Use of antidepressants nearly doubled, increasing from seven percent to 13 percent.

-Among 18 types of drugs used by more than 2.5 percent of Americans, use increased for 11 medication types.

-Significant increases were seen only in people aged 40 and older, not among those 20 to 39.

Increasing use of certain drugs may reflect the growing need to treat conditions associated with being overweight and obese, the researchers said.

Many of the 10 most commonly used drugs in 2010-2011 treat high blood pressure, diabetes and high cholesterol, which are related to diet, exercise and weight, the study authors said. Another drug, omeprazole, is used to treat acid reflux, which can be exacerbated by obesity.

After Zocor, the top 10 included lisinopril (Prinivil), levothyroxine (Levothroid), metoprolol (Lopressor), metformin (Fortamet), hydrochlorothiazide (Aquazide H), omeprazole (Prilosec), amlodipine (Norvasc), atorvastatin (Lipitor), and albuterol (Ventolin, Proventil). Use of all except atorvastatin increased over the study period.

Katz said a healthy lifestyle can prevent most of the chronic diseases these drugs treat.

"Consider the irony. Here in the U.S., we aggressively peddle foods that propagate illness, and drugs to treat the illness that ensues. 'Big Food' and 'Big Pharma' are the winners -- we and our families, the losers," he said.