PhD Oral Exam - Robbie Woods, Psychology

When studying for a doctoral degree (PhD), candidates submit a thesis that provides a critical review of the current state of knowledge of the thesis subject as well as the student’s own contributions to the subject. The distinguishing criterion of doctoral graduate research is a significant and original contribution to knowledge.

Once accepted, the candidate presents the thesis orally. This oral exam is open to the public.

Abstract

Depression is the most prevalent psychiatric condition among individuals seeking bariatric surgery for severe obesity (BMI ≥ 40.0 kg/m2; 35.0 with weight-related comorbidities). Following bariatric surgery, depression prevalence and symptom severity drastically reduces. That said, depression that persists or worsens after bariatric surgery is associated with poorer weight loss outcomes. Psychiatric conditions, e.g., depression, are routinely evaluated during a preoperative psychosocial evaluation when determining suitability for a bariatric procedure. This includes a clinical interview that may be supplemented with screening tools for assessing psychiatric symptoms, e.g., depression. Screening tools are more frequently administered after bariatric surgery in order to monitor how well individuals are adjusting after the procedure. Despite the ubiquity of depressive symptom screening tools, there is a limited understanding of their use in a bariatric population. The current dissertation sought to address the current gaps in the literature regarding depressive symptom screening tools in the bariatric population. The first study consisted of a systematic review and meta-analysis that included 46 studies that examined the evolution of depressive symptoms after individuals had undergone bariatric surgery. Results from the meta-analysis determined that the magnitude that depressive symptoms decreased was similar at 6-, 12-, and 24-months after surgery. The second study examined whether the responses to items within a common depressive symptom screening tool clustered together in a bariatric cohort. This study performed both exploratory and confirmatory factor analyses within two groups and found a model consisting of three subscales was the most appropriate for screening depressive symptoms pre- and post-surgery. The final study examined whether reductions of depressive symptoms overall or within specific subscales were associated with weight loss outcomes. The total and subscale change-scores were tested separately in the association with percent excess-body weight loss. Only the reduction of negative perception features of depression was linked to greater weight loss. Taken together, these studies can inform healthcare professionals about the typical evolution of depressive symptoms up to 24 months after surgery, as well as the depressive symptoms that might be potential targets for intervention if weight loss following bariatric surgery is suboptimal.