What are the long-term impacts of depression on short-term memory?
Answered by: Laurence Messier, Master's student in Neuroscience
But what about short-term memory specifically? Several studies have shown that depression can affect short-term memory, the type of memory that allows us to retain a limited amount of information in a short period of time. For example, a group of researchers published their study in 2013 and found that the more severe the depressive symptoms, the more difficult it was for the participants to perform a task that assessed their associative memory abilities5.In this task, participants were shown a series of images representing objects that are seen daily. However, there was a catch: some of the images could either appear only once, or appear twice, or could be replaced by a similar image. The participants' goal was to remember whether or not they had already viewed an image or if they had already viewed a similar one during the task.In this task, participants were shown a series of images representing objects that are seen daily. However, there was a catch: some of the images could either appear only once, or appear twice, or could be replaced by a similar image. The goal of the participants was to remember whether or not they had already seen an image or if they had already seen a similar one during the task. After analyzing the results, the researchers observed that the depressed participants did less well than the other participants, indicating that their condition had an impact on their memory.
But how are memory and depression related? Unfortunately, science has not yet fully answered this question. However, our brains can give us some clues to find an answer! Indeed, several research groups that have studied the subject have found that several parts of the brain are altered physically and in their functioning in the context of depression6. For example, the prefrontal cortex, the part of our brain that is located just behind our forehead, does not function the same way in people living with depression as it does in people without a psychiatric illness6. In fact, this part of the brain, which is associated with short-term and long-term memory, shows reduced activity in these individuals. Another example is the hippocampus, a tiny structure found in each hemisphere of our brain. Indeed, it is atrophied in people living with depression7. Although it is not yet known whether this illness has an influence on the size of the hippocampus or vice versa, one thing is certain: this brain structure plays an important role in learning, but also in memory6. Indeed, the hippocampus allows the brain to transform short-term memories in order to store them in our long-term memory8. It is worth noting that even after the remission of a depressive disorder, the hippocampus does not tend to return to its previous size9. This may partially explain why memory-related symptoms may persist even after all other depressive symptoms have resolved10.