Exposure therapy is a technique in behavior therapy used to treat anxiety disorders. It involves the exposure of the patient to the feared object or context without any danger, in order to overcome their anxiety. Procedurally it is similar to the fear extinction paradigm in rodent work. Numerous studies have demonstrated its effectiveness in the treatment of anxiety disorders such as PTSD and specific phobias.
Exposure-based therapy may be effective in preventing the progression from acute stress disorder to post-traumatic stress disorder, according to a report in the June 2008 issue of Archives of General Psychiatry.
The use of exposure as a mode of therapy began in the 1950s, at a time when psychodynamic views dominated Western clinical practice and behavioral therapy was first emerging. South African psychologists and psychiatrists first used exposure as a way to reduce pathological fears, such as phobias and anxiety-related problems, and they brought their methods to England in the Maudsley Hospital training program. 
Joseph Wolpe (1915–1997) was one of the first psychiatrists to spark interest in treating psychiatric problems as behavioral issues. He sought consultation with other behavioral psychologists, among them James G. Taylor (1897–1973), who worked in the psychology department of the University of Cape Town in South Africa. Although most of his work went unpublished, Taylor was the first psychologist known to use exposure therapy treatment for anxiety, including methods of situational exposure with response prevention—a common exposure therapy technique still being used. Since the 1950s several sorts of exposure therapy have been developed, including systematic desensitization, flooding, implosive therapy, prolonged exposure therapy, in vivo exposure therapy, and imaginal exposure therapy.
Exposure therapy is based on the principle of respondent conditioning often termed Pavlovian extinction. The exposure therapist identifies the cognitions, emotions and physiological arousal that accompany a fear-inducing stimulus and then tries to break the pattern of escape that maintains the fear. This is done by exposing the patient to progressively stronger fear-inducing stimuli.  Fear is minimized at each of a series of steadily escalating steps or challenges (a hierarchy), which can be explicit ("static") or implicit ("dynamic" — see Method of Factors) until the fear is finally gone. The patient is able to terminate the procedure at any time.
There are three types of exposure procedures. The first is in vivo or “real life.” This type exposes the patient to actual fear-inducing situations. For example, if someone fears public speaking, the person may be asked to give a speech to a small group of people. The second type of exposure is imaginal, where patients are asked to imagine a situation that they are afraid of. This procedure is helpful for people who need to confront feared thoughts and memories. The third type of exposure is interoceptive, which may be used for more specific disorders such as panic or post-traumatic stress disorder. Patients confront feared bodily symptoms such as increased heart rate and shortness of breath. All types of exposure may be used together or separately.
While evidence clearly supports the effectiveness of exposure therapy, some clinicians are uncomfortable using imaginal exposure therapy, especially in cases of PTSD. They may not understand it, are not confident in their own ability to use it, or more commonly, they see significant contraindications for their client.
Flooding therapy also exposes the patient to feared stimuli, but it is quite distinct in that flooding starts at the most feared item in a fear hierarchy, while exposure starts at the least fear-inducing.
Generalized anxiety disorder
There is empirical evidence that exposure therapy can be an effective treatment for people with generalized anxiety disorder, citing specifically in vivo exposure therapy, which has greater effectiveness than imaginal exposure in regards to generalized anxiety disorder. The aim of in vivo exposure treatment is to promote emotional regulation using systematic and controlled therapeutic exposure to traumatic stimuli.
Exposure therapy is the most successful known treatment for phobias. Several published meta-analyses included studies of one-to-three hour single-session treatments of phobias, using imaginal exposure. At a post-treatment follow-up four years later 90% of patients retained a considerable reduction in fear, avoidance, and overall level of impairment, while 65% no longer experienced any symptoms of a specific phobia.
Agoraphobia is an example of a phobia that has been successfully treated by exposure therapy. Agoraphobia is a fear of being alone, leaving home, feeling trapped or being embarrassed or helpless. Such fears can be very debilitating in themselves, and in addition patients often worry about showing anxiety and losing control in public.
Post-traumatic stress disorder
Virtual reality exposure (VRE) therapy is a modern but effective treatment of post-traumatic stress disorder (PTSD). This method was tested on several active duty Army soldiers, using an immersive computer simulation of military settings over six sessions. Self-reported PTSD symptoms of these soldiers were greatly diminished following the treatment.,  Exposure therapy has shown promise in the treatment of co-morbid PTSD and substance abuse.
There are a number of organizations of behavior therapists around the world. The Association for Behavior Analysis International (ABA) offers a certification in behavior therapy  to therapists who demonstrate competence in exposure therapy.
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