Neurobiology of anxiety and anxiety disorders : a thesis presented in partial fulfilment of the requirements for the degree of Master of Veterinary Studies (MVS) at School of Veterinary Science - Tāwharau Ora, Massey University, Palmerston North, New Zealand

Abstract

Anxiety is one of the most conserved affective states across sentient organisms, yet its biological, historical and pharmacological aspects remain incompletely integrated. This thesis examines anxiety across three domains to establish a unified framework that links anxiety as a physiological affective state and anxiety disorders as psychopathological disorders. An in-depth literature review was conducted to analyse findings across disciplines namely anatomy, pharmacology, psychology, and neuroscience, to dissect anxiety and anxiety disorders, how they are manifested in different species and what underlying changes occur. Each domain revealed conceptual boundaries that reflect both the progress and the persistent gaps in anxiety research. The absence of a clear, cross-disciplinary distinction between physiological anxiety and anxiety disorders has limited translational research, particularly across species. This thesis addresses that gap by integrating historical, neuroanatomical, and psychopharmacological evidence to propose a unified, biologically grounded framework applicable across humans, canines, non-human primates, and rodents. What emerges is not a disorder of circuits gone wrong, but of circuits that cannot stop being correct, and it is precisely that distinction that future research, across species and disciplines, must be built upon.