For this research, the team did a meta-analysis of 44 different studies, which included a cumulative of just over 2,000 people with a history of major depressive disorder, plus over 2,200 controls without a history of depression.

They were specifically looking for any notable differences in the participants’ reactions to positive, negative, or neutral stimuli. Some of the assessments involved happy, sad, or neutral faces, for instance, while others involved reacting to different words.

One of the findings was that healthy participants were more quick to respond to stimuli in general, than those with a history of depression. Further, and most notably, participants with a history of depression spent more time on the negative emotional stimuli than the positive, compared to controls.

As the study’s lead author, Alainna Wen, Ph.D., explains in a news release, “Our findings suggest that people who have a history of depression spend more time processing negative information, such as sad faces, than positive information, such as happy faces, and that this difference is greater compared to healthy people with no history.”

These findings are significant, given that this tendency to spend more time processing negative information could be a risk factor for relapse. “Because more negative thinking and mood and less positive thinking and mood are characteristic of depression, this could mean that these individuals are at a greater risk for having another depressive episode,” Wen explains.