Depression is a condition characterized by sadness and other symptoms, which are implicated in a persistent style of thinking referred to as depressive rumination. The analytical rumination hypothesis argues that depression is an adaptive response to complicated, personal problems, and that rumination involves an analysis of these problems. This analytical rumination has two stages: first, depressive symptoms promote causal analysis (i.e., considering why the problems happened). Causal analysis then leads to problem-solving analysis (i.e., finding ways to deal with problems), which in turn reduces depression. The empirical studies in this dissertation collectively test whether the nature of depressive thinking is consistent with the analytical rumination hypothesis. In Chapter 2, I investigated the temporal order of sadness and the stages of analytical rumination by asking participants to write about their personal problems. This writing paradigm promoted sadness and causal analysis, but not problem-solving analysis, suggesting that depressive symptoms coincide with causal thinking. In Chapter 3, I explored whether emotions during writing were related to analytical thinking by modifying the paradigm to isolate the impact of other factors (i.e., personal experience with the problem and its valence). These factors could not fully account for emotional changes during writing, suggesting that analytical thinking played a role. Analytical rumination is one of several theories of depressive thinking, so in Chapter 4, I conducted a joint factor analysis of four rumination questionnaires and compared the prevalence of the emerging factors. Factors reflecting causal thoughts and problem-solving were most frequently endorsed, even when they were measured in the presence of sadness induced by the writing paradigm in Chapter 5. Furthermore, associations between these factors and depressive symptoms were consistent with the stages of analytical rumination. Overall, my findings suggest that depressive thinking focuses on understanding and solving problems, and it may have functional implications for depression. / Dissertation / Doctor of Philosophy (PhD) / Depression is a mental health condition in part characterized by sadness and changes in thinking. One evolutionary perspective argues that depression is a response to complicated, personal problems, and that symptoms of depression, like sadness, help individuals think through their problems. According to this perspective, depressive thinking is analytical, and it involves causal thinking to identify why the problems happened and problem-solving to find potential solutions. In my dissertation, I examine whether individuals engage in causal thinking and problem-solving when they are sad or depressed. My experiments assess whether writing about personal problems promotes sadness and causal thinking, and they examine the impact of analytical thinking on changes in sadness during writing. Because the evolutionary perspective is one of several theories on depressive thinking, I also use a psychometric method to integrate these theories and to examine how causal thinking and problem-solving are linked with sadness and other depressive symptoms.

The mood-as-input hypothesis was developed to explain perseverative worry. Based on this model, it is predicted that the amount of time individuals persist on tasks is based on their mood, and this hypothesis may explain the tendency for some individuals to engage in prolonged episodes of depressive rumination. However, surprisingly few studies have examined the applicability of the hypothesis to depressive rumination. Based on the mood-as-input hypothesis, it was predicted that persistence at a rumination task would be greatest in a "sad mood" condition paired with an "as many as can" (AMA) stop rule because individuals with depression have a difficult time assessing when to disengage from the rumination process. Participants were randomly assigned to one of three mood conditions (positive, negative, or neutral) through the use of movie clips from the Lion King and one of two stop rules conditions (as many as can or feel like stopping). Participants then completed the Catastrophic Interview Procedure (CIP), in which they were asked to recall a situation or event in their life that is associated with a depressed mood. More steps are indicative of greater rumination. Contrary to previous literature on the topic, there was no significant interaction between mood and stop rules on depressive steps; however the current study was the first to identify rumination as a predictor of variance after controlling for mood and stop rules indicating that the natural tendency to engage in rumination is an additional relevant variable in a basic perseveration task.