According to the principle of extinction, the fear response decreases or weakens when the patient is exposed to the feared situation and does not undergo a fear experience or arousal (Porter et al.). The therapist first determines and ranks the patient's feared situations according to severity (Porter et al., 2006). Distress is measured by the Subjective Units of Distress

Scale at a range of 0 to 100 from minimal to severe. The person should remain in the situation until his distress level decreases to at least half. Exposure should not terminate when he is at the peak anxiety level or experiencing a panic attack. Terminating exposure at this point will reinforce the phobia. It can also develop aversive arousal that can lead to escape behaviors. These behaviors can lessen the probability of overcoming the feared situation, increase the timetable of therapy or end too early (Porter et al.).

Issues

The five variations are therapist-directed vs. self-directed, massed vs. spaced, graduated vs. intense, endurance vs. controlled escape, and attention vs. distraction (Porter et al., 2006). The therapist-directed type has proved more effective on less motivated or educated patients. The self-directed type, on the other hand, appears more suitable to independent more educated patients. Most therapists begin with the self-directed type before moving to the self-directed type (Porter et al.).

In vivo exposure often involves long and continuous sessions or short and interrupted ones (Porter et al., 2006). Its overall effectiveness, dropout and relapse rates have, however, not been evaluated. A study conducted on two groups of patients with agoraphobia, who underwent 10 weekly and 10 daily sessions, respectively, found the massed or long and continuous-sessions type more effective. A similar study of 36 patients, however, found this type effective when used immediately as well as at follow-up six months later. A further study tested the responses of a distraction group and a focused group. Post-test showed that 54% of the distraction group had higher end-state functioning against the 25% of the focused group. The focused group response, however, went up to 63% against that of the distraction group, which lowered to 42% at follow-up six months later....

The finding also implied that patients with agoraphobia use distraction more often than safety signals or safety behaviors. Safety signals are usually people or things, which make the person feel safe, secure or comfortable in a given feared situation. He brings these things with him in those situations. Problem occurs when he perceives these objects are the source of his safety or comfort and, thus, defeat treatment. Safety behaviors, on the other hand, are gestures, which reduce anxiety during treatment, such as crossing the legs, touching something or sitting down to avoid a fall. These are escape behaviors, which prevent the patient from learning how to tolerate his anxiety. They also reduce the intended connection with the feared situation and, ultimately, negate the effect of therapy (Porter et al.).
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