The work is part of a provocative and growing body of research that documents how polypharmacy — the use of multiple prescription drugs at the same time — has risen in the United States. The number of Americans taking at least five prescription drugs at the same time rose sharply between 1999 and 2012, and the elderly are particularly at risk for dangerous interactions between drugs.
The study examined drugs that list possible adverse side effects including depression and suicide, but that does not mean the link was always well-characterized — or that people should stop taking a drug that could be helping them. Painkillers and antidepressants were listed, which could be related to underlying reasons for the depression.
Dima Qato, an assistant professor at the University of Illinois at Chicago College of Pharmacy who led the study, said that while there has been attention to social factors that increase risk for depression, there is often little attention to the role of medications.
“We know polypharmacy is growing, we know it is not always promoting good health and longevity in patients, and we know a lot of drugs have certain adverse effects — and one of them is depression and suicidal symptoms,” Qato said. “As a pharmacist, when a patient comes in and reports depressive symptoms, I just think it's really important to think about what other medications they are on.”
The study analyzed a detailed survey of thousands of American adults taken every two years between 2005 and 2014, in which people opened their medicine cabinets and showed researchers all the prescription drugs they had taken in the last month. They were also assessed for depression.
Over the decade, Qato and colleagues found that 37 percent of U.S. adults, on average, took medications associated with a side effect of depression.
The team also found that the number of people taking at least three medications that carried a potential side effect of depression increased over the survey time period, from 6.9 percent in the 2005-2006 survey to 9.5 percent in 2013-2014. The rate of depression tripled in people taking at least three medications with a possible side effect, compared to people taking no drugs with that side effect.
The researchers found the same pattern, even when excluding people who were taking antidepressants. Taking multiple medications that didn't carry a depression risk was not associated with increased depression.
Michael Steinman, a professor of medicine at the University of California at San Francisco, pointed out that for many drugs, the risk of depression as a side effect is not well understood and may even be controversial. Studies have shown mixed evidence, for example, about a link between commonly taken high blood pressure drugs called beta blockers and depression.
But even if doctors don't have definitive proof that a particular drug is causing a depression, the study is a reminder that physicians should consider the role of medications — particularly for patients on multiple medications associated with increased risk of an adverse side effect, which the study shows are commonly used.
“It should up the ante about having the conversation about whether a medication is really helpful,” Steinman said. “A lot of times, people stay on medications for a long time. It's easier to continue than to stop them. It's a reminder to always be thinking: does this person really need this medication?”
Qato said that pharmacists stick labels on pill bottles, warning that drugs increase the risk of drowsiness, that people should take food or not drink alcohol with a certain medication, but that many patients — and doctors — may be unaware of the depression risks of certain prescription drugs.
“Even if the same doctor is prescribing drugs, the fact is that it’s really difficult — there’s no software that tells a doctor, 'your patient is on three drugs that predispose them or are associated potentially with depression or suicidal symptoms,'” Qato said.