SLC6A4 and depressive disorder: High incidence of MI is seen in patients with a history of MDD; this association is due to dysregulation of the serotonin transporter (SERT), causing increased activation of platelets in depression, leading to a higher risk of coagulopathy and coronary arterial obstruction, platelets have the largest concentration of serotonin in the body and cannot synthesize their own serotonin [15].