Dissertation: 31.10.2023: Depression and Self-knowledge: Behavioral and Brain Responses of Reflected Self-evaluation and Implicit Self-esteem in Sub-clinical Depression (Lou)
Depression is a common but serious mental disorder that affects how a person thinks of himself or herself. Under the influence of depression, people may possess a distorted, negative view of themselves, despite the fact that this negative view is not necessarily in line with reality. Through three separate but interlinked studies, the current research explored depression-related behavioral and brain responses to the processing of negative self-knowledge.
The research began with a literature review (Study I), summarizing previous findings in the field of self-knowledge and depression. According to the review, negative self-knowledge can be reflected in direct self-evaluation, where depressed individuals evaluate themselves negatively from their own point of view. This negative self-evaluation can result in low self-esteem that is conscious to the individuals themselves. In addition, the altered brain responses suggest that the negative self-evaluation is probably driven by abnormal cognitive control during the evaluation.
Building on these findings, two research topics were proposed in the review. First, the depression-related reflected self-evaluation, where individuals evaluate the self by reflecting on how they believe they are seen by others, was scarcely investigated. Second, previous behavioral findings on depression-related unconscious self-esteem were incongruent, necessitating the use of neuroimaging methods to provide more informative evidence.
The two proposals were addressed later in two empirical studies (Study II and III). In Study II, functional magnetic resonance imaging (fMRI) was used to compare behavioral and brain responses in reflected self-evaluation between individuals with sub-clinical depression, represented by participants with enhanced depressive symptoms, and individuals without depression, represented by control participants without or with few depressive symptoms. Results from this study showed that the sub-clinically depressed participants rated themselves less positively and more negatively than the control participants did, regardless of whose perspective they took. Interestingly, the engagement of temporo-parietal junction, which is typically observed during the use of theory of mind ability (for example, in this study, taking others’ perspective to evaluate the self), was found only in the control group during the reflected self-evaluation. The lack of temporo-parietal junction engagement in the sub-clinical depression group suggests a weak theory of mind usage in this population when they were asked to evaluate themselves through others’ opinions.
In Study III, electroencephalogram (EEG) was employed to compare brain responses between individuals with and without sub-clinical depression during a task measuring implicit self-esteem. Results from this study revealed opposing brain responses between these two groups of participants, although their behavioral performance did not differ significantly. For the sub-clinical depression group, they exhibited larger brain responses when the self was unconscious associated with negative versus positive personality trait adjectives, while the opposite was observed for the control group. The result suggests that the self-is-negative association involves more voluntary attention and greater cognitive control during the task, thus it is probably more congruent with implicit self-esteem in the sub-clinically depressed participants.
Findings from these studies support Beck's cognitive theory by showing that depression significantly influences various aspect of individuals’ understanding of themselves. Furthermore, such influences can be found not only among clinical depression but also sub-clinical population bothered by enhanced depressive symptoms.
Depression poses a significant social and economic burden worldwide. Negative self-knowledge, such as excessive self-criticism, is connected to suicide commitment in depression. Therefore, the impact of negative self-knowledge affects not only the depressed individuals themselves but also a broader social network connected to them, such as their family and community. This research provides a deeper comprehension on behavioral and brain responses to negative self-knowledge in depression. It can help us better understand the symptoms of this disorder, and may serve as a steppingstone for future academic and applied research aiming to improve the self-knowledge in depression.
MA (Sci.) Yixue Lou defends her doctoral dissertation in the subject "Depression and self-knowledge: Behavioral and brain responses of reflected self-Evaluation and implicit self-esteem in sub-clinical depression" on 31 October 2023 at 12 noon. Opponent Senior Research Fellow Mikko Peltola (University of Tampere) and Custos Professor Paavo Leppänen (Ä¢¹½Ö±²¥). The public defense will be held in English.
The dissertation can be read at .
