Depression is a psychiatric condition defined by consistently low mood, low self-esteem and loss of interest in normally enjoyable activities. About 20 percent of people worldwide suffer from major depressive disorder, the clinical name, at some point during their lifetime.
This is the first time a positive cognitive effect has been seen in people with major depressive disorder. The researchers suggest that these patients process information more systematically and analytically than their chipper counterparts. They might unconsciously put more effort into their decisions because they desire control of their environment.
The finding conflicts with other research suggesting depressed people are worse at mental tasks, because they get distracted by thoughts of their problems. Previous studies have shown they perform better when asked not to think about their problems.
In this experiment, 15 people with major depressive disorder, 12 recovering from the disease and 27 individuals without mental health problems were asked to screen 40 candidates and choose the best one for a secretary position. The participants were given only one chance to offer the job, and couldn't go back to re-evaluate a previously seen candidate. Each candidate they saw was ranked in relation to candidates they had seen previously.
The participants with major depressive disorder performed the task better than either the recovering group or the healthy group, choosing candidates about two ranks better -- so the second or third best candidate, compared with the fifth best choice most often chosen by the other two groups.
They made better choices because they searched about five minutes longer before making their decision, the researchers say. The depressed participants spent a longer time on the task because they set a higher threshold of acceptable applicant quality, though they weren't consciously trying any harder to do well.
These new results seem to agree with the theory that depression could increase some mental abilities because of a more analytical thought process and a need to have control over their environment. Decision-making abilities, like those tested in the secretary task, are involved in everyday tasks, like grocery shopping and dating.
Because the scientists didn't find the same effect in the recovering group, who were still suffering from mild depression, it isn't likely that the improvement would be the same in non-clinical cases of depression.
"We found effects for participants still reporting clinical levels of depression but not for those participants who — although still reporting higher levels of depression than healthy individuals — showed indication of recovery," the authors write in a forthcoming issue of the Journal of Abnormal Psychology. "This suggests that — at least in sequential choice — only an acute and severe state of depression leads to changes in strategic behavior."