1. Investigating Euthymia in Bipolar Disorder and Neurochemical Mechanisms of Ketamine Infusions in Treatment-Resistant Depression
- Author
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Njau, Stephanie Njeri
- Subjects
Neurosciences ,Bipolar Disorder ,Emotion Regulation ,Hierarchal Clustering ,Ketamine ,Magnetic Resonance Spectroscopy ,Treatment-Resistant Depression - Abstract
Bipolar disorder (BD) and major depressive disorder (MDD) are debilitating neuropsychiatric disorders affecting millions of people worldwide. Despite the success of medications and psychotherapy in alleviating symptoms, challenges remain in achieving and maintaining remission. In BD, a key therapeutic goal is to reach a state of euthymia, characterized by reduced intensity and frequency of symptoms or no symptoms at all. However, even in euthymia, subtle emotion regulation difficulties often persist, suggesting the illness remains active. Emotion dysregulation in BD is associated with abnormalities in brain regions involved in emotion processing and regulation, including the prefrontal cortex, amygdala, anterior cingulate cortex, hippocampus, insula and striatum (M. L. Phillips & Swartz, 2014; Strakowski et al., 2005). In Chapter 2, I explore functional abnormalities within the emotion regulation network in euthymic BD and their relationship to subclinical symptoms and clinical characteristics of the disorder. Specifically, this study investigates cognitive-emotion regulation processes in the context of negative stimuli. In Chapter 3 and 4, I address the effects of subanesthetic ketamine on neurochemical disturbances in MDD. In this disorder, a subset of patients, approximately 30%, do not achieve remission despite multiple pharmacotherapy trials, a condition known as treatment-resistant depression (TRD). Subanesthetic ketamine has shown promising rapid antidepressant effects in TRD, yet the underlying neurochemical mechanisms remain unclear. I investigated these mechanisms by utilizing proton magnetic resonance spectroscopy (1HMRS) to measure in vivo neurochemistry of the dorsal anterior cingulate cortex (dACC), a region implicated in MDD pathophysiology. Chapter 3 describes a study where sixty volunteers with TRD received a single intravenous infusion of subanesthetic ketamine. 1HMRS was used to measure levels of glutamate and GABA, along with additional biochemical compounds associated with MDD pathophysiology or treatment, including N-acetylaspartate, N-acetylaspartylglutamate, Creatine, Phosphocreatine and Choline-containing compounds. In Chapter 4, I extend the experiment to explore the effects of repeated ketamine infusions in fifty volunteers with TRD. A summary of literature pertinent to each study presented in this thesis is provided in Chapter 1. Collectively, the findings from this dissertation could lead to improved therapeutic strategies and enhanced patient outcomes in both BD and MDD.
- Published
- 2024