Major depressive disorder is a mood disorder characterized by a sustained period of depressed mood and a markedly diminished interest or pleasure in nearly all activities, a state known as anhedonia. The condition has a complex etiology, involving the interaction of genetic vulnerabilities, neurobiological dysregulation, and environmental factors. From a biological perspective, it is associated with measurable alterations in neurochemistry, particularly involving neurotransmitter systems such as serotonin, norepinephrine, and dopamine, which are crucial for regulating mood and cognitive function. Diagnosis requires the presence of persistent symptoms that significantly impair the ability to function in daily life. Management strategies are multimodal, typically incorporating behavioral therapies designed to modify thought patterns and activities, alongside pharmacological interventions aimed at correcting underlying neurochemical imbalances.