This document summarizes depression. It begins by defining depression as a mental state of low mood and loss of pleasure. It then outlines the main topics that will be covered, including the theories of depression, prevalence, forms of depression, signs and symptoms, causes, management, and side effects of medication. The document discusses the different types of depression like major depression and seasonal affective disorder. It also explores the causes of depression such as bullying, personality, and substance use. Finally, it provides an overview of how to overcome depression through psychological treatment, staying active, and managing sleep, thoughts, and irritability.