The aim of this book is to provide a comprehensive review of the use of Transcranial Direct Current Stimulation (tDCS) in different psychiatric conditions. Here we review tDCS clinical studies employing different types of design (from single-session tDCS studies to randomized clinical trials) as well as studies evaluating the impact of tDCS in neurophysiological, behavioral and brain imaging outcomes.  Although the understanding about physiological foundations and effectiveness of clinical therapies of psychiatric diseases has been considerably increased during the last decades, our knowledge is still limited, and consequently psychiatric diseases are still a major burden to the individual patient and society.