The most common therapeutic intervention in medicine is the writing of a prescription. It is especially true in psychiatry as pharmacotherapy has become its mainstay treatment. With over half of the approved drugs having serious adverse effects that were not detected before the approval, it is therefore important to study post-marketing drugs in order to ensure the safety of a drug. The benefits and risks of a psychotropic drug could be studied through using psycho pharmaco epidemiological methods, a science underlying post-marketing drug surveillance. It delineates how psychotropic drugs are prescribed and utilized, investigates reasons underlying prescriptions, and assesses outcomes and variables which may affect these outcomes. This review covers the introduction and development of psycho pharmaco epidemiology, specifically to its scope and limitation, examples of studies published in the past years, and its future perspectives.