Addiction medicine is a medical specialty that deals with the treatment of addiction. The specialty often crosses over into other areas, since various aspects of addiction fall within the fields of public health, psychiatry, and internal medicine, among others. Incorporated within the specialty are the processes of detoxification, rehabilitation, harm reduction, abstinence-based treatment, individual and group therapies, oversight of halfway houses, treatment of withdrawal-related symptoms, acute intervention, and long term therapies designed to reduce likelihood of relapse.

 The term dual diagnosis is used to describe the comorbid condition of a person considered to be suffering from a mental illness and a substance abuse problem. There is considerable debate surrounding the appropriateness of the term being used to describe a heterogeneous group of individuals with complex needs and a varied range of problems.

 Forensic psychiatry is a sub-specialty of psychiatry. It encompasses the interface between law and psychiatry. Some practitioners of forensic psychiatry have taken extra training in that specific area. In the United States, one year fellowships are offered in this field to psychiatrists who have completed their general psychiatry training. Such psychiatrists may then be eligible to sit for a board certification examination in forensic psychiatry.

 Psychosomatic medicine is an interdisciplinary medical field studying psychosomatic illness, now more commonly referred to as psychophysiologic illness or disorder, whose symptoms are caused by mental processes of the sufferer rather than immediate physiological causes. These syndromes are classified as neurotic, stress-related and somatoform disorders by the World Health Organization in the International Statistical Classification of Diseases and Related Health Problems.