I would like to first and foremost acknowledge the contribution from all study participants for contributing with their time and providing valuable data for our research. I am very grateful to Professor Vidar M. Steen, my main supervisor, for including me in his research group, for allowing me the chance to take my PhD and the time to mature. I am also grateful to Professor Ingrid Melle, my co-supervisor, for her extensive knowledge of clinical areas and statistics. She has, without doubt, challenged me the most, asking critical questions, not letting me settle for anything less than my very best. Also, I would like to thank Silje Skrede and Professor Erik Johnsen, my other two co-supervisors, for their valuable inputs. From the TOP group in Oslo, I would like to extend my deepest gratitude to Professor Ole Andreassen for his time, comments for improving the articles, and in general for sharing his immense knowledge. Words cannot describe how deeply grateful I am for having psychiatrist Ingrid Dieseth and clinical psychologist Carmen Simonsen as collaborators and friends. With their positive attitudes and patience for all sorts of questions, they are truly the ideal combination for anyone venturing in the fields of biological psychiatry and neurocognition. I am also thankful to Professor Ingrid Agartz and postdoc Kjetil Jørgensen for navigating me through the fascinating world of neuroimaging. Kjetil has been like a co-supervisor for me, with his patience, steadiness, and expertise. I have genuinely appreciated our long discussions, even those at 2 o'clock in the night. Furthermore, I would like to thank all previous and present members of the Martens group for practical and social input during my years in the group. From the Statistical Department at Haukeland University Hospital, I also have to thank Professor Geir Egil Eide for introducing me to mixed-effects models and for double-checking the analyses. 7 My sincere thanks to Professor emeritus Knut Wester, as he was the one who first introduced me to research back when I was a medical student, and who encouraged me in perusing this PhD. Over the years he has always been available for both PhD-related discussions, but also for discussing any problems related to life in general. My clinical supervisor, Mildrid Clementsen, from my years as a resident doctor at Sandviken Hospital also deserves a huge thank, as she has been there through all the "ups and downs" in this PhD, giving wisdom and comfort when needed. Nevertheless, the most important and inspirational people in my life are my family. I wish to sincerely thank my husband, Åsmund, for his endless love and support. I am also eternally grateful for all the support and help from my mother, Sarva. This study would never have seen daylight had it not been for my mum and my husband. Finally, I owe my two children, Isak and Ivar the world. They have been there with their smiles, warm hugs,