SLC6A4 and Compulsive behaviors: Treatment with escitalopram in patients with TS + OCD and pure OCD (n = 13) resulted in a significant reduction of SERT binding in all investigated brain areas including caudate, putamen, thalamus, hypothalamus, midbrain, pons, and mesial temporal cortex (p values between 0.0409 and <0.0001 depending on the brain region) with differences ranging from 19 to 78% (for further details see Table 3, and Figs 1 and 2).