Increased Temporal Discounting in Social Anxiety Disorder Normalizes after Oxytocin Treatment

CONSORT flow diagram and check list in the online suppl. section “Material”; see www.karger. com/doi/10.1159/000495259 for all online suppl. material) in which 33 medication-free patients with SAD (25 females; age 31.21 ± 11.43 years) and 37 healthy controls (CTL; 31 females; age 34.46 ± 14.45 years) with no current or past physical or psychiatric illness self-administered intranasal OXT (24 IU) or placebo (PLC). The participants were first tested on a social interaction task (the results have been reported elsewhere). Then, they performed a temporal discounting task and a reward valuation, with the latter serving to control for nonspecific anxietyrelated changes in reward processing. Anxiety and depression symptoms as well as social connectedness were measured via questionnaires (see also in the online suppl. section “Results” and online suppl. Table S1). All procedures contributing to this work complied with the ethical standards of the relevant national and institutional committees on human experimentation and with the Helsinki Declaration of 1975, as revised in 2008. A mixed design analysis of variance with the between-subject factors “treatment” (OXT, PLC) and “group” (SAD, CTL), the within-subject variable “relative difference” between soonersmaller and later-larger options (0.5 to 75%), and the proportion of patient choices (later-larger) as dependent variable yielded significant main effects of relative difference (F(3.57, 235.59) = 89.02, p < 0.01, ƞ2 = 0.57; Fig. 1a) and treatment (F(1,66) = 6.17, p = 0.02, ƞ2 = 0.09) as well as a trend-to-significant effect of group (F(1,66) = 3.36, p = 0.07, ƞ2 = 0.05). There were no further interactions (all p values > 0.17). Thus, participants chose the later-larger option more often when there was a greater relative difference in sooner-smaller/later-larger magnitudes. OXT significantly increased the patient choices (later-larger) across all participants. Separate analyses in the OXT and PLC groups revealed that SAD patients showed more impulsive preferences under PLC compared to CTL (F(1,34) = 4.45, p = 0.04, ƞ2 = 0.12), while there was no such difference after OXT treatment (F(1,32) = 0.34, p = 0.56, ƞ2 = 0.01). This pattern of results was confirmed in an additional analysis with the discounting parameter k as dependent variable, demonstrating a main effect of treatment (F(1,64) = 5.52, p = 0.02, ƞ2 = 0.08) and a trend-to-significant effect of group (F(1,64) = 3.78, p = 0.06, ƞ2 = 0.06; Fig. 1b). Interestingly, across all groups, social connectedness positively correlated with the proportion of patient choices in the PLC condition (r(36) = 0.30 p = 0.07; OXT: r(35) = 0.16, p = 0.36), indicating that individuals with less social connections less often restrained from choosing the sooner-smaller option. This is in line with proposals that reduced social connectedness may lead to decreased cognitive control, since social support is a robust stress buffer, and the experience of social exclusion impairs self-regulation [7]. There was no significant main or interaction effect of treatment in the valuation control task (see also online suppl. section “Results” and online suppl. Table S2), indicating that OXT did not alter the valuation of rewards options.