People with mild depression may benefit from taking antidepressants, suggests a new analysis of past studies that compared symptoms in people on the drugs to those given drug-free placebo pills.

Some earlier reports had suggested that antidepressants generally only improve mood in people with severe depression.

But that might be because those studies weren't precise enough to pick up on smaller changes in symptoms that can still make a difference for people with milder forms of the disease, researchers say.

"I think there's a valid concern ... that if someone has not-that-severe depression that hasn't lasted that long, maybe it will get better itself or with therapy," says Dr David Hellerstein, from the New York State Psychiatric Institute and Columbia University, who worked on the study.

Still, he says the question of whether or not to prescribe medication shouldn't necessarily come down to how severe the depression is but rather how long symptoms have lasted.

People with "transient depression" that will improve with diet or exercise or after a few weeks of therapy "shouldn't be taking the risk of being on meds," he says.