More people in the United States are on antidepressants, as a percentage of the population, than any other country in the world. And yet the drugs’ efficacy has been hotly debated.

Some believe that the short-term benefits are much more modest than widely thought, and that harms may outweigh benefits in the long run. Others believe that they work, and that they can be life-changing.

Settling this debate has been much harder than you might think.

It’s not that we lack research. Many, many studies of antidepressants can be found in the peer-reviewed literature. The problem is that this has been a prime example of publication bias: Positive studies are likely to be released, with negative ones more likely to be buried in a drawer.

In 2008, a group of researchers made this point by doing a meta-analysis of antidepressant trials that were registered with the Food and Drug Administration as evidence in support of approvals for marketing or changes in labeling. Companies had to submit the results of registered trials to the F.D.A. regardless of the result. These trials also tend to have less data massaging — such as the cherry-picking of outcomes — than might be possible in journals.