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`THE EFFECT OF TRANSCRANIAL MAGNETIC STIMULATION ON DEPRESSION AND THE ASSOCIATED OLFACTORY DYSFUNCTION by Hannah Clare Taalman A thesis submitted to the Center for Neuroscience In conformity with the requirements for the degree of Master of Science Queen’s University Kingston, Ontario, Canada (September, 2017) Copyright ©Hannah Clare Taalman, 2017 Abstract Introduction: Depression negatively impacts olfactory functioning and as such, olfactory dysfunction has been found in individuals with depression. Expansions of this research have demonstrated an improvement in olfactory functioning after successful pharmaceutical and psychotherapy treatments for depression. However, it is unknown if intermittent theta burst stimulation (iTBS), a form of transcranial magnetic stimulation (TMS) has a similar effect. Objectives: The current study examined the olfactory functioning and depression severity in depressed individuals before and after iTBS, comparing them to non-depressed controls. We hypothesized that depressed individuals would have significantly poorer olfactory functioning compared to controls before treatment, but little to no difference between after successful treatment. We also predicted that depression severity and olfactory dysfunction were negatively correlated. Methods: We recruited 20 depressed individuals receiving iTBS and 9 non-depressed controls. The olfactory function of depressed patients was tested before and after treatment using Sniffin’ Sticks Extended Test (examining olfactory threshold, discrimination, and identification). Depression severity was also evaluated. Controls were tested in the same manner with a 5-6 week waiting period in lieu of iTBS. Results: Both the comparison of olfaction before and after treatment in depressed patients and with controls found no significant differences. An effect of age (p<0.05) and baseline depression severity (p<0.05) were found in the depressed group, with younger and less severely depressed individuals having significantly better olfactory functioning than their counterparts both before and after treatment. There were a number of significant correlations between depression severity and olfactory discrimination, identification, and total olfaction score at both time points. Discussion: While no significant difference was found between the depressed and control groups or within the depressed group, the impact of depression severity provided support for the assumption of a reciprocal relationship. The significant difference between younger and older depressed participants ii highlights the limitation of age present in the study that may have contributed to the lack of significant differences. Overall, the relationship between depression and olfaction has the potential to be an important part of early diagnosis, examination of treatment progression, and on quality of life of depressed individuals. iii Co-Authorship Dr. Roumen V. Milev of the Department of Psychiatry at Queen’s University contributed to the design and execution of the study, as well as the preparation of this document. iv Acknowledgements I owe my deepest gratitude to Dr. Roumen Milev for his supervision, guidance, and support. You have been a source of great inspiration and have helped me carve out a path toward my future career. It is a pleasure to thank Dr. Felicia Iftene, Dr. Ruzia Jokic, and Dr. Alina Marin for their guidance, Dr. Casimiro Cabrera-Abreu, Dr. Dusan Kolar, Joanne Bresee, Teresa Garrah, and Linda McGarry for their help with patient recruitment. It was an honour for me to have had the opportunity to work and learn from these amazing individuals. I am indebted to all of the individuals who participated in this study for giving me their time, trust, and noses in order to make this research possible. I am grateful to Queen’s University, the Centre for Neuroscience Studies, and Dr. Milev for the funding that made this project possible. I would also like to thank and acknowledge my coworkers in the Centre for Neuroscience Studies along with my family and friends for their support and encouragement throughout this process. To my friend Hannah, thank you for continued criticism and feedback on the draft versions of this thesis. I cannot promise it will be the last piece of scientific writing I force you to read, but I nonetheless appreciate your input and criticism that has helped me become a better writer. v Table of Contents Abstract ..........................................................................................................................................................ii Co-Authorship .............................................................................................................................................. iv Acknowledgements ........................................................................................................................................ v List of Figures ............................................................................................................................................... ix List of Tables ................................................................................................................................................. x List of Abbreviations .................................................................................................................................... xi Chapter 1 : Introduction ................................................................................................................................. 1 1.1 General Overview ................................................................................................................................ 1 Chapter 2 : Literature Review ........................................................................................................................ 3 2.1 Introduction.......................................................................................................................................... 3 2.2 Psychiatric and Mood Disorders .......................................................................................................... 3 2.2.1 Major Depressive Disorder ........................................................................................................... 3 2.2.1.1 MDD Comorbidity ................................................................................................................. 4 2.2.1.2 MDD Prevalence and Age ..................................................................................................... 4 2.2.1.3 MDD and Gender .................................................................................................................. 5 2.2.2 Bipolar Disorder ........................................................................................................................... 6 2.3 Treatment of Depression ...................................................................................................................... 8 2.3.1 Pharmacological Treatment .......................................................................................................... 9 2.3.1.1 Pharmacological Treatment of MDD .................................................................................. 10 2.3.1.2 Pharmacological Treatment of BD ...................................................................................... 11 2.3.1.3 Limitations in Pharmacological Treatment ......................................................................... 12 2.3.2 Psychotherapy Treatment ........................................................................................................... 13 2.3.2.1 Psychotherapy Example: Cognitive Therapy ...................................................................... 14 2.3.3 Transcranial Magnetic Stimulation ............................................................................................. 15 2.4 Olfaction ............................................................................................................................................ 17 2.4.1 The Olfactory Pathway and Processes ........................................................................................ 18 2.4.2 Olfactory Dysfunction ................................................................................................................ 19 2.5 Depression and Olfaction .................................................................................................................. 20 2.5.1 Olfaction and Depression: The Brain Regions Between the Two .............................................. 20 2.5.2 Olfactory Dysfunction in MDD and BD .................................................................................... 21 2.5.3 Treatment for Depression and the Impact on Olfaction ............................................................. 23 2.5.3.1 Neuroplasticity and Olfaction.............................................................................................. 25 vi 2.6 Limitations and Future Directions ..................................................................................................... 27 2.6.1 Limitations in the Literature ....................................................................................................... 27 2.6.1.1 Methodology: Olfactory Measure ........................................................................................ 27 2.6.1.2 Methodology: Experimental Design .................................................................................... 28 2.6.1.3 Methodology: