Psychopharmacology is the study of drugs that change a person's mood, behavior or way of thinking. According to Science Daily, these drugs include stimulants and anti-depressants, as well as other medications.
The American Society of Clinical Psychopharmacology is a professional organization that promotes education and research in the field of psychopharmacology. They help connect researchers with subjects for clinical trials, in order to learn more about psychotropic drugs, their affects on people and how well these drugs treat psychiatric disorders. The ASCP states that any physician who prescribes psychotropic drugs is considered a psychopharmacologist, because they must have a full understanding of how the drugs affect patients in order to provide successful treatment.