Behavioral and neural dissociation of social anxiety and loneliness

Background Loneliness is a public health concern with detrimental effects on physical and mental well-being. Given phenotypical overlaps between loneliness and social anxiety, cognitive behavioral interventions targeting social anxiety might be adopted to reduce loneliness. However, it is still elusive whether social anxiety and loneliness share the same underlying neurocognitive mechanisms. The current study aimed at investigating to what extent known behavioral and neural correlates of social avoidance in social anxiety are evident in loneliness. Methods We used a pre-stratified approach involving 42 participants with high and 40 control participants with low loneliness scores. During functional magnetic resonance imaging, the participants completed a social gambling task to measure the subjective value of engaging in a social situation and responses to positive and negative social feedback. Results Uni- and multivariate analyses of behavioral and neural data replicated known task effects across groups. However, although lonely participants were characterized by increased social anxiety, loneliness was associated with a response pattern clearly distinct from social anxiety. Specifically, Bayesian analyses revealed moderate evidence for equal subjective values of engaging in social situations and comparable amygdala responses to social decision-making and striatal responses to positive social feedback in both groups. Conversely, lonely participants showed significantly altered behavioral responsiveness to negative feedback and reduced striatal activity, whereas striatal-hippocampal connectivity was increased compared to controls. Conclusion Our findings suggest that loneliness is associated with altered emotional reactivity to social situations rather than behavioral tendencies to withdraw from social interactions. Thus, established interventions for social anxiety should be adjusted when targeting loneliness.