70 Chapter 4 Exposure intervention The participants engaged in two 90-minute public-speaking exposure sessions delivered one week apart in accordance with the protocols developed by Rodebaugh and colleagues (Rodebaugh et al., 2013; Smits, Rosenfield, Davis, et al., 2013). The sessions were standardized with respect to exposure length (6-8 minutes), preparation time (max. 5 minutes), reaction of the experimenter (neutral), and the availability of notes and speech topic. On the morning of the first day, the participants received psychoeducation about SAD and exposure, with the first session starting after four hours. In both sessions, psychoeducation was repeated and personalized harm expectancies and goals were assessed. Then, the participants presented their prepared speech in front of a therapist, two confederates, and a camera. They reviewed their videotaped performance afterwards together with the therapist. The therapists were psychology students in their last year of training (BA and MA level) trained and supervised by experienced, board-certified psychologists (M.H.M.H. and M.K). To guarantee adherence to the protocol, the therapists were instructed to fill out a checklist of all protocol components and to report any deviations from the protocol. The checklists and reports on deviations showed that 96.3% of the sessions were delivered in accordance with the protocol. Outcome measures Within-session fear (primary outcome) Participants rated their fear levels on a subjective units of distress (SUD) scale ranging from 0: No fear to 100: Extreme fear (Wolpe & Lazarus, 1966). SUDs were collected after psychoeducation (initial SUD), immediately prior to each exposure session (baseline SUD), immediately prior to the speech (start SUD), every two minutes during, and immediately after the speech (endpoint SUD). Symptom severity (secondary outcome) Social anxiety symptoms were assessed with the Social Phobia Scale (SPS; (Mattick & Clarke, 1998)), a self-report measure assessing the fear of being observed or watched during social or performance situations. The scale has shown good internal consistency ((Mattick & Clarke, 1998); α = .94; Dutch translation; (Beurs, Tielen, & Wollmann, 2014), α = .91, current study α = .86). Participants completed the SPS at baseline, after the second exposure session (post-treatment) and at the one-month follow-up (FU) assessment.
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