One in six American adults take psychiatric drugs, a new study reveals.

Researchers mined data from a national survey on drug use across the United States in 2013.

They found more than 5.3 million people admitted long-term use of antidepressants, anxiolytics, sedatives, hypnotics, and/or antipsychotics.

Highest rates were detected among women, elderly people, and white people.

Given that the data was self-reported, the researchers believe this is a woeful underestimation of the true state of drug-use in America.

More than 5.3 million people admitted using psychiatric drugs in a new study

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Women were more likely than men to use psychiatric drugs, according to the figures compiled by the Institute for Safe Medication Practices.

Drug use also became more prevalent with age: a quarter of 60-85-year-olds reported using prescription drugs, as opposed to 9 percent of adults aged 18 to 39.

And white adults were far more likely to report psychiatric drug use (20.8 percent) compared to black adults (9.7 percent), Hispanic adults (8.7 percent) and Asian adults (4.8 percent).

Eight of 10 adults taking psychiatric drugs reported long-term use, defined as three or more prescriptions filled in 2013 or a prescription started in 2011 or earlier.

The study was led by Thomas Moore of Virginia's Institute for Safe Medication Practices, in collaboration with Dr Donald Mattison of Risk Sciences International in Ottawa, Canada.

Consulting the 2013 Medical Expenditure Panel Survey to calculate percentages of drug use, they looked at three classes of psychiatric drugs: antidepressants; anxiolytics, sedatives and hypnotics; and antipsychotics.

Around 17 percent of people reported filling one or more prescriptions.

The most common refills were for an antidepressant, which 12 percent of adults use long-term.