Aleksovski B, et al. - This research was formulated in order to identify and assess the mechanisms of SSRI-induced changes in platelet reactivity in non-responding patients with Recurrent Depressive Disorder (RDD) and life-long exposure to antidepressants. In order to detect SSRI-reduced platelet function for research purposes or systematic correlations with other biochemical parameters, the microscopic evaluation could prove to be beneficial. Findings unveiled complex mechanisms involved in SSRI-reduced platelet function in non-responding RDD patients, with the inclusion of combined effects of lower platelet serotonin content, high fluctuations in plasma serotonin concentration and abnormal α-AR function.