Background: The brain rapidly responds to affective processing and neural responsivity can separate anxiety disorder patients from healthy individuals. Psychiatric treatment also alters brain responsiveness however, the brain’s temporal dynamics during treatment remain unknown. Here, patients with social anxiety disorder (SAD) were treated with cognitive-behavioral therapy (CBT) and functional magnetic resonance imaging (fMRI) assessments were performed before, during and after intervention.

Methods: Forty-six SAD patients received a 9-week Internet-delivered CBTand symptoms were assessed weekly using the Liebowitz social anxiety scale (LSAS-SR). MRI was acquired at 4 time-points (2 baselines, mid- and post-treatment). Blood-oxygen level-dependent(BOLD-fMRI) was performed while patients viewed negative facial expressions. BOLD-fMRI data was reviewed manually by classifying signal from noise, all subjects contributing with complete data.

Results: Patients improved slightly from baseline to mid-treatment (P<.001, Cohen’s d=0.34) on the LSAS-SR, but more so from mid- to post-treatment (P<.001, d=1.46). Whole-brain neural responsivity decreased from baseline to post-treatment (False Discovery Rate, FDR P<.005) in the medial prefrontal cortex, precuneus and amygdala/parahippocampus. However, no changes (FDR P>.05) from mid- to post-treatment were found, suggesting that the early alterations accounted for the effect. Furthermore, early response reductions were positively associated with symptom improvement from pre-post treatment (Pearson’s r=.50, P<.001).

Conclusions: This is, to our knowledge, the first study assessing early and late psychiatric treatment changes in the brain. Interestingly, altered neural responsivity in limbic and default-mode network regions preceded self-reported alleviation of social anxiety. Understanding the brain’s temporal dynamics and subsequent modification of behavior may be highly important for future clinical neuroimaging research.