What is the difference between a Psychiatrist vs. Psychologist?

Which is the right Expert Witness?

By Sanjay Adhia, M.D.

Both are addressed as “Doctor” but with very different meanings.

Many litigants and even some attorneys I have worked with use the terms interchangeably as if they were as interchangeable as spelling of the same word, like behavior and behaviour (British spelling).

Psychiatrists are Physicians, Psychologists are Not

A psychiatrist is a medical doctor that can diagnosis mental disorders including substance use disorders and prescribe medications. A psychiatrist can order and interpret labs and imaging such as a Brain MRI. Some psychiatrists provide psychotherapy and are able to do psychological testing.

Psychiatrists complete medical school where they are exposed to all the medical specialties from surgery to radiology. They also learn about anatomy, physiology, pharmacology and other disciplines. After medical school they complete a four-year psychiatry residency which includes rotations in Internal Medicine, Neurology as well as of course Psychiatry.  The exposure to psychiatry is varied and includes inpatient, outpatient, consult (medical hospital), addictions, child and possibly geriatric settings.


After completing the residency, some psychiatrists will sub-specialize. Some examples include child psychiatry, addiction psychiatry, and psychosomatic (consult-liaison) psychiatry. There are other specialties that are available for psychiatrists and other doctors such as Brain Injury Medicine and Sleep Medicine.

Forensic Psychiatry: Unique Additional Training and Rigorous Specialty Board-Certification

Forensic Psychiatry is a unique sub-specialty.  According to AAPL (American Academy of Psychiatry and the Law), forensic psychiatry is the discipline “in which scientific and clinical expertise is applied in legal contexts involving civil, criminal, correctional, regulatory or legislative matters, and in specialized clinical consultations”.

Currently, a one-year fellowship is required to obtain Board Certification in Forensic Psychiatry. The fellowship includes training in correctional psychiatry and performing medico-legal evaluations as an expert witness. There are didactics on the legal system and landmark cases. Forensic psychiatrists have training and typically more experience in performing detailed evaluations, writing medico-legal reports and testifying.

A Psychologist’s Training and Licensing

Psychologists do not attend medical school. They receive training in diagnosing mental disorders, psychological testing and providing psychotherapy. Except in a few states in limited circumstances, psychologists do not prescribe medicine. They do not receive training to interpret brain imaging or labs. Some psychologists receive extra training to become Forensic Psychologists which deals with the interface between psychology and the law.  Neuropsychologists receive extra training in performing detailed neurocognitive testing.

Many cases will require a psychiatrist, particularly if medical records, lab results, or neuroimaging are involved.  For example, the medical experience of a physician was absolutely necessary for the case studied in an interesting case study about Competency to Stand Trial.   Quite a few cases may benefit from having both a psychiatrist and a psychologist.  Occasionally, there may be cases when a psychologist may be better suited.

Please feel free to give me a call. Initial case discussion, up to an hour, is free. Let’s discuss your case and my qualifications.

The American Psychiatric Association has an interesting article on this topic.

Endnote regarding doctors with the designation “DO” (Jane Smith, DO): A physician with the designation DO is the same as an MD. Both have received extensive medical school training and completed a residency. Both an MD and DO can become Board-Certified which reflects Fellowship training in Forensic Psychiatry. Any doctor with DO has the same qualifications, credentials, and training as an MD.

* PhD stands for “Doctor of Philosophy.” In fact, a PhD is granted in many disciplines, though some are in Philosophy. Psychologists can attain a PhD but may or may not be licensed as Psychologists.  An “MD” is a Doctor of Medicine. Philosophers might choose to not attain a Medical License, though some MDs are philosophers.  A third degree, PsyD, Doctor of Psychology, also reflects academic achievement found among licensed psychologists, although the emphasis of training may differ from that of a PhD psychologist.