According to the Diagnostic and Statistical Manual of Mental Disorder (DSM-IV), a specific phobia is characterized by marked and persistent fear of clearly discernible, circumscribed objects or situations. Exposure to the phobic stimulus almost invariably provokes an immediate anxiety response. Most often the phobic stimulus is avoided, although it is sometimes endured with dread. The focus of the fear may be anticipated harm from some aspect of the object or situation. Specific phobia may also involve concerns about losing control, panicking, and fainting that might occur on exposure to the feared object. The level of anxiety or fear usually varies as a function of both the degree of proximity to the phobic stimulus and the degree to which escape from the phobic stimulus is limited. The specific phobia frequently interferes with the individual's daily routine, occupational functioning, or overall quality of life. Some examples of specific phobias include the fear of flying, a fear of snakes, the fear of riding in elevators, a fear of heights, or a fear of enclosed spaces.