Depression. Depression (major depressive disorder or clinical depression) is a common but serious mood disorder. It affects how you feel and think and can affect how you go about your daily life. Some symptoms of depression include feelings of hopelessness and pessimism, irritability, feeling of guilt, worthlessness, or helplessness, Loss of interest or pleasure in hobbies and activities, and thoughts of death, suicide or suicide attempts. Holden shows some of these symptoms in the book.