People suffering from depression tend to confuse past experiences and present thoughts, a new study has found. Researchers from Brigham Young University have determined that the condition can influence memories by blurring distinctions and conflating details. Besides illuminating new treatment strategies, the findings provide new insight into the complex processes that allow us to create and store memories.
Published in the journal Behavioral Brain Research, the study examined the previously established link between depression and poor memory. According to lead author Brock Kirwan, the team wanted to tie depression to specific aspects of the memory process. The hope was that a firm understanding of this relationship might subsequently identify a third, underlying problem.
"That's really the novel aspect of this study — that we are looking at a very specific aspect of memory," Kirwan said, speaking to The Salt Lake Tribune. "What we think is going on is there are physiological changes in the brain that are underlying both depression and these memory problems."
To investigate the link, the team enrolled a number of depressed adults in an experiment. In a computer-aided memory test, subjects were shown a series of objects and asked to remember them. They were then shown a second set of objects and asked to identify them as either old, brand new, or new but very similar to something they had seen before.
While most subjects nailed the distinctions between brand new and old objects, many struggled in identifying an object as different but similar to one seen before. In these cases, the most common incorrect answer was that the second object had been seen before. The results led the researchers to conclude that depression is associated with impaired “pattern separation” — the cognitive process whereby general characteristics are abstracted from one object and mapped onto another.
Together with previous research, the findings shed important light on the physiology behind depression and memory. "There are two areas in your brain where you grow new brain cells," Kirwan explains. "One is the hippocampus, which is involved in memory. It turns out that this growth is decreased in cases of depression."
Today, approximately one in 10 U.S. adults report symptoms of depression. The debilitating condition can exacerbate existing medical complications and lead to short-term disability, decreased productivity, and work absenteeism. The authors of this study hope that a clear relationship between depression, pattern separation, and the hippocampus could inspire future psychiatric research as well as new treatment programs.