Brain serotonin transporter availability predicts treatment response to selective serotonin reuptake inhibitors

Few studies have investigated the predictive value of central serotonin transporter (SERT) availability for treatment response to serotonin reuptake inhibitors (SSRIs). This study used brain imaging to examine the relationship between pretreatment brain SERT availability and transporter occupancy by SSRIs with treatment response in two independent depressed populations. Study 1: Twenty-three patients with major depression underwent a single photon emission computed tomography (SPECT) measurement of brain SERT availability using [ 123I]β-CIT ([ 123I]methyl 3β-(4-iodophenyl) tropane-2β-carboxylate. The SERT availability was correlated with treatment response to fluoxetine (20 mg/day) assessed with weekly Hamilton Depression Rating Scale (HDRS) for 6 weeks. Study 2: The second group included 10 depressed patients who received 6 weeks of paroxetine treatment (20 mg/day) and serial SPECT scans (baseline, during, and after the treatment). In Study 1, higher pretreatment diencephalic SERT availability significantly predicted better treatment response 4 weeks later. Similar results were found in Study 2 and supported Study 1 findings. The data showed that greater occupancy of diencephalic transporters by paroxetine correlated with better treatment response. Higher pretreatment availability and greater occupancy of SERT in diencephalon may predict better treatment course in response to SSRIs.