1. Mohammad Haghighi 1*, Leila Jahangard 1, Hafez Bajoghli 2, Markus Gerber 3, Roumen Kirov 4, Edith Holsboer-Trachsler 5, Serge Brand* 3,5, Zahra Fathirezaie 6, Seyed Hojjat Zamani Sani 6 1 Research Center For Behavioral Disorders and Substances Abuse, Hamadan University of Medical Sciences, Hamadan, Iran 2 Psychiatry & Psychology Research Center (PPRC), Roozbeh Hospital, Tehran University of Medical Sciences, Tehran, Iran 3 Department of Exercise and Health Sciences, Division of Sport Science, University of Basel, Basel, Switzerland 4 Institute of Neurobiology, Bulgarian Academy of Sciences, Sofia, Bulgaria 5 Psychiatric Clinics of the University of Basel, Center for Affective, Stress and Sleep Disorders (ZASS), Basel, Switzerland 6 Shahid Beheshti University,Tehran, Iran Electroconvulsive therapy and aerobic exercise training increased BDNF and improved depressive symptoms in patients suffering from treatment-resistant major depressive disorder BDNF LEVELS HAMILTON DEPRESSIO RATING SCALE Conclusions The pattern of results suggests that, first, ECT, AE and particularly the combination of ECT and AE are promising directions to treat patients suffering from treatment-resistant MDD, and that, second, it remains a matter of debate to what extent BDNF is key and a reliable biomarker for MDD. Contact Serge Brand, PD Dr. phil. Universitäre Psychiatrische Kliniken (UPK), Zentrum für Affektive-, Stress- und Schlafstörungen (ZASS) Wilhelm Klein-Strasse 27, 4012 Basel, Schweiz serge.brand@upkbs.ch Background In search of more effective treatment algorithms for patients suffering from treatment-resistant major depressive disorder (MDD), research has focused on electroconvulsive therapy (ECT) and aerobic exercise (AE). Moreover, brain derived neurotrophic factor (BDNF) seems to be key in MDD. However, no research has investigated ECT and AE treatments concomitantly. The aims of the present study were therefore two-fold: to investigate in a three-arm interventional study the different effects of ECT, ECT and AE, and AE alone in patients suffering from treatment resistant MDD on 1.) depressive symptoms and 2.) BDNF. Method A total of 60 inpatients suffering from treatment-resistant MDD (mean age: 31 years; 31.6% female patients) were randomly assigned either to the ECT, the ECT + AE, or the AE condition. The AE condition consisted of treadmill exercise for 30 minutes, three times a week, with an intensity level of 60-75% of VO2max. Both depression severity and BDNF levels were assessed at baseline (Time 1) and 4 weeks later (Time 2). All patients were further treated with SSRI (Selective Serotonin Reuptake Inhibitor) standard medication. Results BDNF levels increased over time in all three study conditions (Figure 1). After completion of the intervention program, the ECT group showed significantly higher BDNF levels compared to the ECT + AE and the AE conditions. Depressive symptoms decreased in all three study conditions over time (Figure 2). The combination of ECT + AE led to a significantly greater decrease as compared to the ECT or AE conditions alone. BDNF levels were not associated with symptoms of depression (r.50). Fig. 1 Fig. 2