:               Depression is a common debilitating illness impacting more than 280 million people worldwide. It impacts all age groups across all socioeconomic strata and has been designated as a major contributor to the global disability burden. As highlighted by the National Mental Health Survey of India 2015-16, the treatment gap for any mental morbidity stands at around 70-90%. Among those who receive treatment, approximately one-fourth of the patients fail to respond to antidepressants. Despite advances in neurosciences, no single theory can adequately explain the onset and progression of Depression. The broad consensus links MDD with impairment in neural signalling, loss of hippocampal volume, reduction in growth factors such as BDNF, loss of synaptic plasticity and cognitive functions, decline in monoamine neurohormones, and dysregulation of polyamine metabolism. In recent years, the gut microbiota has emerged as a potential player in the pathogenesis of MDD, with evidence suggesting an intricate relationship between gut bacteria and Depression.