The results determined by experts from the Yale School of Medicine were derived from an experiment with 754 men and women over the age of 70, observed from 1998, and every 18 months that followed.
On every check-up the subjects were asked about their medical conditions, and were screened for things such as loss of appetite, sadness, or sleep problems experienced the week before, signs that are considered to be symptoms of depression.
According to CBS News, the results showed that 36 percent of the participants experienced depression at one point, half of which stayed depressed for two consecutive check-ups.
Five percent were determined to have been depressed for all the five check-ups.
Of that percentage, however, scientists determined that more women experienced depression more than men, and were more likely to suffer from it more than once.
"Our findings provide strong evidence that depression is more persistent in older women than older men," said Lisa C. Barry, the study's lead author and associate research scientists in the Yale School of Public Health.
"We were surprised by this finding because women are more likely to receive medications or other treatment for depression."
HealthNews Digest added that Barry felt the need for a follow-up study determining how women respond to conventional antidepressant treatments, as well as the manner by which they are treated.
The study was included in the February Archives of General Psychiatry.
