Individual depressive theories founded on neurobiological information are examined because they hold great relevance to both clinical investigators seeking to create innovative treatments for depression and physicians in everyday practice. One such theory is the proposition that the main underlying issue behind depressive disorders is a deficiency in central monoaminergic function. This theory highlights the importance of addressing the role of neurotransmitters such as glutamate, gamma-aminobutyric acid (GABA), norepinephrine, serotonin, and dopamine, as well as factors like neurocircuitry, neurotrophic factors, and the rhythm of the circadian clock. Major depressive disorder, a severe condition with significant societal and therapeutic implications, necessitates tailored antidepressant treatments. These treatments encompass both pharmacological interventions and emotional therapies, all of which need to be customized based on specific patients and medical circumstances. The understanding of depression is complex and constantly evolving, with various explanations and theories applying only to specific types of depressed individuals while disregarding others. Furthermore, the pathogenesis of depression can undergo significant changes during the disease’s development. This dynamic nature challenges the notion that depression can be characterized by a single hypothesis or theory. Thus, the extensive body of available research highlights the need for a comprehensive approach that incorporates multiple concepts and factors when studying and treating depression. By considering the intricate interplay of various neurobiological elements and personal circumstances, researchers and medical professionals can strive to provide more effective and tailored interventions for individuals suffering from depression.