Depression is one among the most rampant form of psychiatric disorders and a leading cause for morbidity and mortality. Depression should be recognized as a clinical syndrome that is characterised by a cluster of emotional, behavioural, and cognitive features. Depression also poses a significant economic burden to society as it leads to reduced productivity, treatment costs and loss of human life by suicide. Depression is a common problem affecting about 121 million people worldwide. It occurs in persons of all genders, ages, and back- grounds. Depression is almost twice as common in females as males. Depression refers to a wide range of mental health problems which is characterized by enduring sadness, anhedonia, guilt, low self esteem, disturbed sleep, poor appetite, low energy, suicidal thoughts, a lack of libido, fatigue, poor concentration and reduced attention, pessimistic and suicidal tendencies, food intake dysregulation. Clinical evidence supports the fundamental roles of serotonin and norepinephrine, as well as the interactions between these systems in the etiology of depression. In addition, substance P, corticotropin-releasing factor, dopamine, g-aminobutyric acid (GABA), somatostatin, and thyroid-related hormones have been implicated in the pathophysiology of Depression. Many brain regions have been implicated in regulating emotions; we still have a very rudimentary under standing of the neural circuitry underlying normal mood and the abnormalities in mood that are the hallmark of Depression. Depression is associated with a serious impairment of social, marital, and occupational functioning, as well as prominent personal and interpersonal distress