Anxiety is a normal reaction to stress and can be beneficial in some situations. It can alert us to dangers and help us prepare and pay attention. Anxiety disorders differ from normal feelings of nervousness or anxiousness, and involve excessive fear or anxiety. Anxiety disorders are the most common of mental disorders and affect nearly 30% of adults at some point in their lives. But anxiety disorders are treatable and a number of effective treatments are available. Treatment helps most people lead normal productive lives.