Cheng-Ta Li is a professor at National Yang Ming Chiao Tung University and is a division chief at Taipei Veterans General Hospital. Professor Li has been devoted in the field of TRD for over 15 years. Now, he is ranked top <1% in the field of TRD with multi-disciplinary collaborations. Based on the result of Expertscape (2011-2021), he is currently ranked #< 1% (0.77%) in the world in the field of TRD and is the highest among scientists in Taiwan. This book, inviting internationally renowned experts in the field, aims to clarify unsettled issues related to TRD, to provide a better understanding about TRD, and to improve treatment efficacy for TRD.