Depression also known as major depressive disorder (MDD), unipolar depression, and clinical depression, is one of the most common psychiatric disorder in the world affecting more than 300 million people of all ages globally. Depression is a serious disease that can have significant burden or disability in a patients day to day activities and could be possibly life- threatening because of suicidal inclination. Depression is characterized mainly by depressed mood and anhedonia that lasts for at least two weeks. The severity of the disease ranges from mild to severe. There are many different subtypes of depression distinguished by further symptoms and events. The etiology of the disease is considered to be multifactorial due to the combination of genetical, biological, psychological, and environmental factors. Although the exact etiology of depression is still not known, it is believed that in most cases the decreased amount or deficiency of neurotransmitters such as serotonin, noradrenaline, and dopamine in the brain plays a major role in the pathophysiology of the disease. Therefore currently the pharmacological therapies focuses mainly on adjusting the levels of these neurotransmitters in the patient. In this thesis, I will be focusing on the pharmacological treatment of depression; the different types of drugs with their pharmacodynamics effects on the human body and the different outcomes.