Depression is one of the most prevalent and life-threatening forms of mental illnesses associated with significant disability and mortality. Stress can be considered as a major contribution for the development of depressive disorder due to dysregulation of HPA-axis. Although there are multiple pathways that are involved in the pathogenesis of depression, the current antidepressants mainly target monoaminergic pathway. However, therapeutic potential of other pathways is still under investigation. Drugs targeting nitric oxide, cytokines and kynurenine acid pathway might be the drugs of choice in near future. Alzheimer’s disease is a neurodegenerative disorder with progressive dementia. Although basic research in Alzheimer’s disease has made remarkable progress in past 2 decades, currently available drugs are able to improve cognitive symptoms temporarily, and no treatment can reverse, stop, or even slow this inexorable neurodegenerative process. This book dwells on the recently unravelled pathogenetic hypothesis and therapeutics of mental depression and Alzheimer’s disease.