Please note that the content of this book primarily consists of articles available from Wikipedia or other free sources online. Anxiety disorder is a blanket term referring to a variety of mental illnesses, including panic disorder, obsessive compulsive disorder, post-traumatic stress disorder, social anxiety disorder, specific phobias and generalized anxiety disorder. Although anxiety is a normal response to certain situations, anxiety disorders cause abnormal distress that deprives individuals of their ability to perform their everyday tasks and lead a normal life. Learn more about the disorders, their causes and treatment in this book.