OBJECTIVES: Exposure-based cognitive behavioural therapy (eCBT) is an effective treatment for anxiety disorders. Response varies between individuals. Gene expression integrates genetic and environmental influences. We analysed the effect of gene expression and genetic markers separately and together on treatment response. METHODS: Adult participants (n≤181) diagnosed with panic disorder or a specific phobia underwent eCBT as part of standard care. Percentage decrease in the Clinical Global Impression severity rating was assessed across treatment, and between baseline and a six month follow-up. Associations with treatment response were assessed using expression data from 3,233 probes, and expression profiles clustered in a data-driven and literature-driven manner. 3,343,497 genetic variants were used to predict treatment response alone and combined in polygenic risk scores. Genotype and expression data were combined in expression quantitative trait loci (eQTL) analyses. RESULTS: Expression levels were not associated with either treatment phenotype in any analysis. 1,492 eQTLs were identified with q