Physiological psychology is sometimes related to psychiatry, and in fact may end up becoming the parent branch which contains psychiatry. This term is not universally accepted as being official jargon, but the concept behind it is rather clear and it does unify several previously similar areas of research.

As background, psychiatrists are the only doctors of psychology who must have completed medical training (at least in the United States). They are certified as are other medical doctors, and they are able to write prescriptions (subject to standard DEA regulations and limitations). Psychiatrists rarely tend to handle the psychological disorders that are perceived as being caused by physical irregularities; as an example, bipolar disorder is caused by abnormal concentrations of neurotransmitters and is therefore often treated with antidepressant medications that moderate the production or removal of neurotransmitters.

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