Anxiety disorders are a group of mental illnesses that cause people to feel excessively frightened, distressed, or uneasy during situations in which most other people would not experience these same feelings. When they are not treated, anxiety disorders can be severely impairing and can negatively affect a person's personal relationships or ability to work or study. In the most severe cases, anxiety disorders can make even regular and daily activities such as shopping, cooking or going outside incredibly difficult. Anxiety disorders can further cause low self-esteem, lead to substance abuse, and isolation from one's friends and family.
Anxiety disorders are the most common mental illnesses in America: they affect around 20 percent of the population at any given time. Fortunately there are many good treatments for anxiety disorders. Unfortunately, some people do not seek treatment for their illness because they do not realize how severe their symptoms are or are too ashamed to seek help. Furthermore, these disorders are often difficult to recognize for friends, family and even some doctors.
Read more about anxiety at the National Insitute of Mental Health.