Memory and Major Depressive Disorder

by Taylor Martin-LaVache

What is Major Depressive Disorder (MDD)?

Major Depressive Disorder, also known as Clinical Depression is one of the most common mental illnesses. More likely than not, you have been touched by depression, whether that be through a friend, family member, or a personal encounter with the illness. Depression is characterized by decreased interest and concentration, changes in sleep and eating habits, irritability, fatigue, and anhedonia or a lack of interest in activities that one used to enjoy. One is diagnosed with MDD after a prolonged amount of time experiencing these symptoms, and most importantly they are negatively impacting the individual’s life. MDD can often present itself out of thin air, with little to no explanation for its presence, and therefore little hope to eradicate it. When someone experiences a physical injury there is often a clear cause and effect relationship, an estimated recovery time, and effective techniques to aid recovery. Mental illnesses are not as simple.

Memory Issues Associated to MDD

Recall Issues

It has been scientifically proven that people with depression often have a harder time recalling positive and even neutral memories, while their recall for negative memories appears to be typical (Williams et al., 1996). One factor of memory that is often overlooked is its use for predicting the future. For example, if you are planning a trip to the beach you use your memory to remember to pack a towel, sunscreen, and a bathing suit and you can’t forget to pack extra snacks because you remember that last time you packed insufficiently and suffered the consequences of immense hunger. Without your memory, you would not have been able to pack effectively. The same is true for people who have depression. Since they have more trouble recalling positive memories it is challenging or even impossible for them to predict a positive future. Their fully intact negative memories and lack of positive ones exacerbate this phenomenon (Barry et al., 2018). The looming thought that, “I’ve always been miserable, so I will continue to be in the future” is ever present. This makes it difficult for them to feel hope for the future, and may even be a driving force behind suicidal thoughts. This idea can worsen or prolong a depressive episode and most likely make it more difficult for them to escape it.

Autobiographical Memory Specificity

One example of this fact is the intertwined relationship between autobiographical memory and mood disorders like Major Depressive Disorder. Autobiographical memory describes memories pertaining to the self, like specific events or pinnacle experiences. These memories are a combination of both episodic memories (events or episodes of one’s life) and semantic (factual) memories. These memories are often accompanied by heightened emotions and sensory details that allow one to feel as though they are reliving the event. They are often organized in the form of stories as well. There is a strong link between depression and reduced specificity of autobiographical memories. This can lead to poor problem solving and emotion regulation, as well as low emotional support. Since they don’t have all of the details, it is more difficult to make an informed decision. Memories are often used to regulate one’s emotions, since they can reminisce about a happy memory and look forward to more in the future. Due to the lower specificity of these memories and the difficulty recalling positive memories, this technique is either less effective or completely ineffective for someone with depression. Memories are also used as a way to connect with others. Most of our conversations involve recounting past happy memories in specific detail and weaving a story for others. This is how we make our most meaningful connections, so with less specific memories it is more difficult for someone with depression to form these bonds. Therefore, when someone with depression is in need of support, they may not have a strong circle of friends to confide in and rely on (Barry et al., 2018).

Positive Memories and Their Role in Emotion

Positive memories are interpreted as a reward in the brain. The striatum and the medial prefrontal cortex, brain regions involved in the reward processing, respond more to the recounting of positive memories than neutral ones. In addition, the positive emotions experienced and the emotional intensity of the memory are positively correlated to heightened activity in these regions  (Speer et al., 2014). This indicates that depressed individuals are most likely experiencing this rewarding sensation less due to their difficulty recalling positive experiences. In addition, vivid positive memories are linked to higher self-esteem. These individuals tend to have more emotional details than visual details when recalling a positive memory (van Schie et al., 2019). This may indicate a relationship between vivid memories and self-esteem, and may explain why low self-esteem is often associated with depression.

Conclusion

The presence of such a phenomenon shows us that people who live with or suffer from mental illnesses are not in complete control of their situations. Mental disorders used to be, and often are seen now as reversible by naive individuals, but that is simply not the case. Mental illnesses are just as debilitating as physical ones, and they should be treated with the same understanding and care. They are not simply due to a lack of strength or effort as some may believe, and this data proves that fact. The presence of such a deficiency can provide people who do not live with the disorder an explanation for why depressive episodes are so debilitating and hard to escape. Finding out ways in which the depressed brain works differently, that there are scientifically proven blockades in one’s path, can allow depressed individuals to give themselves grace and feel better about taking a bit longer to get to the finish line.