Depression is more than simply feeling unhappy or fed up for a few days or it may seriously continue for long. Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behavior, feelings and sense of well-being. People with depressed mood can feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, ashamed or restless. Depression is a serious mental health condition (mental illness) that has an impact on both physical and mental health, it is not something that you have made up in your head. Learn about depression symptoms, warning signs, and causes, plus what you can do to feel better.