Drugs so frequently list “death” as a possible side effect that the danger has come to seem unremarkable. Currently, more than one third of Americans are taking drugs that come with an increased risk of depression and—whether or not they realize it—patients are feeling the impact.

A paper published today (June 12) in Journal of the American Medical Association analyzed the impact of more than 200 prescription drugs that carry such risks, including hormonal birth control, blood pressure, and heart medications, as well as painkillers. Analysis of surveys of 26,000 American adults from 2005 to 2014, which were collected as part of the US National Health and Nutrition Examination Survey, showed that taking multiple such medications dramatically increased the risk.

The research team, led by Dima Qato, professor of pharmacy at the University of Illinois-Chicago, found that roughly 4.7% of those who don’t take any medication with depression as a side effect have depression, compared to 6.9% of those who take one such drug, and 15.3% of those who take three or more.

Qato warned that few of the drugs come with warning labels, and so millions of people are likely unaware of the risk. “Many may be surprised to learn that their medications, despite having nothing to do with mood or anxiety or any other condition normally associated with depression, can increase their risk of experiencing depressive symptoms, and may lead to a depression diagnosis,” she said in a statement.

Many of the drugs are commonplace and not associated with a risk of depression despite the evidence showing their effects. Earlier research from the same team showed that hormonal birth control is linked with a 70% higher risk of depression (that’s relative risk; it means if 10 women not taking the drugs develop depression, then 17 women on the medication will).

The list of potential side effects that accompanies most prescription drug may seem farcically long, and it can be easy to assume that the ill effects won’t impact you. But the research shows that even seemingly innocuous drugs can have serious harmful effects.