The essential features of generalized social phobia are defined by the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition (DSM-IV), criteria as a marked and persistent fear of most (generally accepted as four or more) social or performance situations in which the patient believes embarrassment could occur as a consequence of exposure to unfamiliar people and/or possible scrutiny by others. The anxiety resulting from the social or performance situation is profound. The avoidance, fear, or anxious anticipation of these situations interferes significantly with the person's daily routine, having a marked impact on occupational functioning and/or social life. The disorder has a lifetime prevalence estimated at up to 13%, with onset typically in the mid-teens, and it is diagnosed slightly more frequently in females than in males. Social phobia tends to be a chronic disorder with periods of exacerbation, with a reported mean duration of illness of approximately 20 years.