78 Chapter 4 The effect of testosterone administration on social anxiety symptoms SAD symptoms decreased from pre- to post-treatment (Mpre = 30.20 vs. Mpost = 28.04), Estimate = -2.22(1.23), t(1,102) = -1.80, p = .074 and significantly so from pre- to FU: Estimate = -7.02(1.23), t(1,102) = -5.70, p < .001 (Mpre = 30.20, MFU = 23.26). There was no group x time interaction: pre-post, Estimate = -0.48(1.23), t(1,102) = -.39, p = .697, pre-FU: Estimate = -2.10(1.23), t(1,102) = -1.70, p = .092, indicating that symptom severity after treatment discontinuation did not show any of the effects of testosterone enhancement on within-session fear. There was no effect of baseline testosterone. Discussion Seeking to test the effects of testosterone-augmented exposure treatment for individuals with SAD, we compared a single exposure session with testosterone supplementation (0.50 mg) to an exposure session with placebo, assessing fear levels in an unenhanced second session and SAD severity after one month. The exposure sessions were successful in reducing fear, HR, and SAD symptoms, independent of group. Foremost, testosterone augmentation was associated with higher peaks followed by a steeper decline in fear at the end of the second unenhanced session. Post-hoc analyses revealed this pattern was most pronounced in participants with higher baseline testosterone and evident in both the enhanced (session 1) and the transfer session (session 2). Peak fear levels in the participants with low basal testosterone remained lower throughout both sessions. Testosterone enhancement did not significantly change SAD symptom severity. Our proof-of-concept results provide preliminary support that testosterone may act on important mechanisms of exposure, meriting further examination of multiple-session testosterone-enhanced exposure therapy for SAD. The effects of testosterone partly coincide with several studies supporting avoidance-reducing and social-approach-facilitating properties of the hormone (Enter et al., 2014; Enter, Spinhoven, et al., 2016; Terburg et al., 2016). Moreover, the SUD patterns (increase prior to a decrease) are in line with Emotional Processing Theory (EPT) positing that fear needs to be activated first and only after prolonged exposure, fear levels will drop. Such reactive pattern is deemed essential for learning and, hence, transfer in the long run (Foa & Kozak, 1986b; Foa et al., 2005). By boosting initial engagement with the feared stimulus, testosterone may affect important learning mechanisms reinforcing transfer (e.g., initial engagement to the feared stimulus in session 1 that transfers to fear levels in a second unenhanced session). Such interpretation is in line with the threat-ap-
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