There are many different types of psychologists, as is reflected by the 56 different divisions of the American Psychological Association (APA). Psychologists are generally described as being either “applied” or “research-oriented”. The common terms used to describe this central division in psychology are “scientists” or “scholars” (those who conduct research) and “practitioners” or “professionals” (those who apply psychological knowledge). The training models endorsed by the APA require that applied psychologists be trained as both researchers and practitioners, and that they possess advanced degrees.
Although clinical psychologists and psychiatrists can be said to share a same fundamental aim—the alleviation of mental distress—their training, outlook, and methodologies are often quite different. Perhaps the most significant difference is that psychiatrists are licensed physicians. As such, psychiatrists often use the medical model to assess mental health problems and rely on psychotropic medications as the chief method of addressing mental health problems—although many also employ psychotherapy as well. Clinical psychologists receive extensive training in psychological test administration, scoring, interpretation and reporting. These tests help to inform diagnostic decisions and treatment planning. For example, in a medical center, a patient with a complicated clinical presentation who is being seen by a psychiatrist might be referred to a clinical psychologist for psychological testing to aid in diagnosis and treatment. In addition, psychologists (particularly those from PhD programs) spend several years in graduate school being trained to conduct behavioral research, including research design and advanced statistical analysis. While this training is available for physicians via dual MD/PhD programs, it is not typically included in medical education. Conversely, psychiatrists, as licensed physicians, have received training more broadly in other areas such as medicine and neurology and may bring this knowledge to bear in identifying and treating medical or neurological conditions that can present similarly to psychiatric diseases.
Psychologists generally do not prescribe medication, although in some jurisdictions psychologists have limited prescribing privileges. Clinical and other psychologists are experts at psychotherapy (typically clinical psychologists are trained in a number of psychological therapies, including, behavioural, cognitive, humanistic, existential, psychodynamic, and systemic approaches), and psychological testing (e.g. including neuropsychological testing). In three US states (Illinois, Louisiana, and New Mexico), some psychologists with post-doctoral pharmacology training have been granted prescriptive authority for certain mental health disorders upon agreement with the patient’s physician.