The main recognized types of anxiety disorders include panic disorder, social anxiety disorder, generalized anxiety disorder and specific phobias, according to WebMD. These disorders are serious mental illnesses that cause so much overwhelming worry and fear that they impair a person's ability to lead a normal life.
Symptoms vary depending on the type of disorder, but in general, symptoms of an anxiety disorder include sleeplessness, shortness of breath, dizziness, dry mouth and heart palpitations, notes WebMD. A person may also experience cold or sweaty hands or feet, nausea, muscle tension and general feelings of panic or fear.
The exact cause of anxiety disorders is unknown, as of 2015, but scientists agree they are mostly caused by a combination of factors, such as brain changes and environmental stress or trauma, explains WebMD.