Mood-Congruent Memory and Depression: A Vicious, Unrelenting Cycle

Imagine this: You enter your dorm room after a long, difficult day, and you’re in a bad mood. You’ve been in the library all afternoon, you’re drenched to the core from walking back in the rain, and you still have what feels like an actual mountain of homework left. As you’re unpacking your bag, events from the day run through your mind, and they’re all negative: the test that didn’t go so well, the lunch that wasn’t great, the workout that felt particularly hard… the list goes on. Your day was not entirely bad, yet you’re only able to remember the not-so-great moments.

If you can relate to the above story, you’ve experienced the effects of mood-congruent memory, which is the idea that the memories we retrieve tend to be consistent with our current emotional state. This explains why people who are in a bad mood recall negative memories, and the same goes for all types of moods. Interestingly, mood-congruency affects people’s attention, too, as is mentioned in this post on attentional biases. However, for the purpose of my blog post, I’m going to focus on memory. Essentially, individuals’ moods dictate the types of memories to which they have access, which in turn reinforce their current mood state. This can be helpful when the positive memories contribute to the happy mood, and it’s generally not a big deal when the bad mood is temporary, since the negative memories will likely soon be replaced by more cheerful ones. That being said, the reciprocal relationship between mood and memory can be dangerous when the unhappy mood state is constant. Consider, for instance, individuals who suffer from depression.

Mood-congruent memories play a harmful role in reinforcing depressed people’s negative moods, creating a somewhat inescapable cycle. This means that depressed individuals are especially likely to have depressing memories –– memories that contribute to their already-depressed state, perpetuating this cycle and maintaining the depression. Why does this occur?

Mood-congruent memory, in general, can be explained by the cognitive psychology principle of encoding specificity, or the concept that memory retrieval –– accessing stored memories –– is easiest when the retrieval context matches the context in which the encoding –– the initial formation of the memory trace –– took place. When we encode memories, we also take in information about the encoding context. Emotions are a form of contextual information, so when an individual’s current emotional state is similar to his/her emotional state at the time of encoding, the memory trace is most accessible (McBride & Cutting, 2019). This is why mood-congruent memories powerfully affect depressed people: the depressed mood upon retrieval matches that at the time of encoding the memory, so these individuals are biased toward retrieving depressing memories. https://twitter.com/ap_psychology/status/1072132699605950466 It is easiest to access memories when the mood during encoding matches that upon retrieval. Interestingly, existing research suggests that these mood-congruent memories need not even be accurate to be retrieved by depressed people.

In one study on mood-congruent memory and depression, Howe and Malone (2011) compared depressed and non-depressed subjects’ false memory for different types of words. The researchers utilized the Deese-Roediger-McDermott (DRM) paradigm , presenting participants with positive, negative, neutral, and depression-relevant word lists. Then, the subjects took a memory test and here’s where the study became really interesting: as opposed to the non-depressed participants, depressed subjects had a significantly greater number of false memories for the critical lure –– a non-list word that fit the category of the list –– when the word was depression-relevant (Howe & Malone, 2011). In other words, both groups performed similarly when the words were positive, negative, and neutral, yet the depressed participants were more likely to incorrectly believe that they’d seen a word when it was related to depression.

I use these findings to highlight two significant points relating to mood-congruent memory: first, considering that depressed participants had higher false memory for depression-relevant –– but not negative –– critical lures, it is clear that these false memories were specific to the depressed mood state; second, if depressed individuals are not only accurately remembering depressing memories, but are also falsely remembering them, this means that they are particularly vulnerable to the harmful effects of mood-congruent memory. Why do mood-congruent memories seem to have such a strong impact on depressed people? https://www.ft.com/content/b02fd44e-13ba-11e2-9ac6-00144feabdc0 Depressed individuals’ bias toward retrieving depressing memories in conjunction with their inability to suppress these memories maintain this dangerous mood-memory cycle. Well, some psychologists have hypothesized that depressed individuals have a higher resting automatic activation of depression-related stimuli (Roediger et al., 2001, as cited in Joormann et al., 2009). By activation, I mean that depression-related information –– words, in the case of the above study –– is so relevant for depressed individuals that it quickly brings forth other, similar information, such as the depression-relevant critical lure, as demonstrated above (Joormann et al., 2009). Additional findings suggest that depressed individuals are often unable to suppress these harmful (and sometimes false) mood-congruent memories. So, in addition to their increased access to true and false depressing memories, depressed individuals have a hard time getting rid of the memories, which means they remain stuck in the cycle of depression. Let me elaborate:

Existing research reveals that depressed individuals’ tendency to ruminate is related to their difficulty blocking out depressing (or mood-congruent) and irrelevant memories. Rumination is a major symptom of depression, and it refers to repetitive dwelling on negative thoughts. In the case of depression, someone who suffers from this mood disorder might constantly think about the cause of his/her depression, the reasons why his/her life is difficult, etc. It’s easy to jump to the conclusion that depressed individuals can choose to control whether they dwell on these harmful thoughts and memories, but I’d like to challenge this potential assumption. https://www.everydayhealth.com/depression/depression-and-ruminative-thinking.aspx Rumination is a common symptom of depression. In a study conducted by Joormann and Gotlib (2008), depressed and non-depressed participants were instructed to memorize two lists of emotional words, some of which were negative and some of which were positive. Then, subjects took a test […]

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