Major depressive disorder is one of the most common mental disorders. Research by Hill and colleagues (2019) has shown that people with depression display attenuated responses to positive and negative stimuli. In this paper, depression is defined as mood disorder, characterized by anhedonia, an inability to feel pleasure, and a reduced state of mood. By measuring the late positive potential (LPP) the researchers evaluated the three most prominent theories of emotional reactivity: negative potentiation, positive attenuation, and emotional-context insensitivity. LPP is a measure of event-related potential; it measures the extent of attention that a stimulus elicits. This study used a structural equation model that distinctified responses as being attributed to depression versus comorbidities such as anxiety. In addition, this study used the Depression Anxiety Stress Scale to distinguish depression from other comorbidities. The three types of stimuli used were pleasant (kitten), unpleasant (snake), and neutral (rubber band). The images were divided into two blocks that were equal in terms of arousal level. Participants were exposed to their assigned block of images twice, with each round of images delivered in a random order. To measure LPP, participants were fitted for an electrode cap that recorded EGG response. Major findings include that depression is associated with lower reactivity to pleasant and unpleasant stimuli. In addition, it was found that this reduction in emotional reactivity was not present in neutral stimuli. It was stated that these findings are specific to depression, not anxiety. Because reduced emotional reactivity was seen with pleasant and unpleasant stimuli, these findings support the emotional-context insensitivity hypothesis.
The significance of the present study is that it discusses characteristics that result from depression, but it also alludes to factors that may contribute to depression. Depression is a mood disorder that can also be associated with feeling disconnected and feeling alone. While the stimuli in this study used images such as animals and objects, the idea of attenuated emotional reactivity has the potential to apply to facial expressions. Every day, people are presented with countless opportunities to connect with others through non-verbal communication (i.e. facial expressions). Without being explicit, facial expressions are a way for people to feel like they understand another and that they are connected. For example, imagine you are at a park and you see something humorous. You might look around and see that someone else is smiling at the same humorous event. If you chose to share that understanding of laughter and humor, you might find yourself feeling better than if you were alone. For that reason, it is significant to discover attenuated emotional reactivity because it may be a factor in social disconnectedness.
To expand on the idea of social connectedness, research by Santini and colleagues (2020) has demonstrated a relationship between lack of social connectedness and depression. The focus of this research was to explain the unique, specific roles that social disconnectedness and isolation had on depression and anxiety. For the purpose of this paper, I will focus on depression. Using a sample of 3005 adults, significant findings include that greater social disconnectedness may lead to greater feelings of isolation and thus, lead to increased depressive signs. Social disconnectedness was scaled by the participant’s amount of social interactions. A score less than zero indicated less than average social disconnectedness and a score greater than zero indicated an above average social disconnectedness. Isolation was scaled by support from family and friends and emotions such as feeling isolated or alone. This was scored as in social disconnectedness. While this paper included isolation, this role of social connectedness is extremely relevant. To relay this to the present study, reduced emotional reactivity to pleasant and unpleasant stimuli may also contribute to feelings of isolation and in turn, this has the potential to predict and encourage depressive symptoms. Going back to the humorous event and park example, a reduced emotional reactivity to the humorous event also reduces the likelihood of understanding why the other person is laughing. In turn, this disconnection between perception has the potential to affect understanding stimuli and it may reduce opportunities to experience shared perception or in other words, it may lead to greater social disconnectedness.
Together, these pieces discuss aspects that result from depression and factors that may predict depression. These findings suggest that the result of depression (i.e. attenuated emotional reactivity) and predictor factors of depression (i.e. social disconnectedness and isolation) are similar to a cycle of not understanding others and feelings of isolation. To address this, further research on the specific perception of stimuli should be evaluated. For example, it is important to explore if despite showing attenuated emotional reactivity, are individuals with depression more likely to view unpleasant, pleasant, or neutral stimuli as more negative? Understanding this would contribute to the understanding that depression requires a holistic and integrated approach, as it is a multidimensional disorder that is influenced by emotional reactivity, social connectedness, and perhaps even perception.
References
Hill, K., South, S., Egan, R., Foti, D. (2019). Abnormal emotional reactivity in depression:
Contrasting theoretical models using neurophysiological data. Biological Psychology, 141, 35-43. https://doi.org/10.1016/j.biopsycho.2018.12.011
Santini, Z., Jose, P., Cornwell, E., Koyanagi, A., Nielsen, L., Hinrichsen, C., Meilstrup, C.,
Madsen, K., Koushede, V. (2020). Social disconnectedness, perceived isolation, and symptoms of depression and anxiety among older Americans (NSHAP): a longitudinal mediation analysis. Lancet Public Health, 5, e62-e70. https://doi.org/10.1016/S2468-2667(19)30230-0
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