One drug comes out top in a large analysis, external of how effective antidepressants are at keeping patients free of symptoms of depression.
Escitalopram performed best at preventing patients from relapsing in a study involving nearly 10,000 people prescribed different medications for up to a year.
Two other pills - agomelatine and duloxetine - came next, while prozac (also known as fluoxetine) ranked just below them.
Experts stress the findings don't mean that everyone with severe depression should switch to escitalopram, or that other antidepressants aren't any good, because all the drugs can work and each has its pros and cons.
Depression is common, affecting around one in six people in the UK. With the right treatment and support, people can make a good recovery although for some their depression can return.
To prevent relapse, doctors already recommend people stay on antidepressants for at least six months after depression ends, and then taper off gradually.
The new analysis, published in The Lancet Psychiatry, looked at previous studies comparing the effectiveness of more than a dozen common antidepressants in total.
The differences found were modest and experts say longer studies are still needed to find out more.
There are many contributing causes to depression and a variety of ways to treat it, including drugs and talking therapies.
