Dopamine transporter binding in social anxiety disorder: The effect of treatment with escitalopram

Objectives Social Anxiety Disorder (SAD) is characterised by persistent fear of social or performance situations. Functional brain imaging has provided evidence that the dopamine system plays a significant role in mediating SAD. This study measures the effects of pharmacotherapy on dopamine transporter (DAT) binding in patients with SAD.

Methods Adult subjects meeting DSM-IV criteria for generalised SAD were studied before and after 12 weeks of pharmacotherapy with the serotonin specific reuptake inhibitor (SSRI) escitalopram. DAT SPECT using [I-123]-FP-CIT was performed at baseline, and repeated at 12 weeks. Striatal DAT binding was measured as the specific uptake ratio (reference region: cerebellum) and results before and after therapy were analyzed with Statistical Parametric Mapping (SPM).

Results The study included 14 patients (9 male) with a mean (SD) age of 41 (13) years. The subjects Liebowitz Social Anxiety Scale (LSAS) scores were significantly decreased (p=0.004) following pharmacotherapy. A significant correlation (R²=0.46, p < 0.01) was found between improved symptoms and increased DAT binding in the left caudate. In addition two clusters of decreased DAT binding were observed in the left and right caudate nuclei following therapy.

Conclusions Existing striatal DAT imaging literature based on volume of interest analyses is contradictory, possibly due to heterogeneous striatal effects. The correlation found between clinical response and increased DAT binding in the left caudate, may reflect serotoninergic inhibition of dopamine function following SSRI therapy. Decreased DAT binding at other sites in the left and right caudate nuclei probably reflect a drug effect, unrelated to therapy.

Research Support Medical Research Council of South Afric