The Science of Neuropsychiatry: Past, Present, and Future

The renewed clinical field of neuropsychiatry aims, as its name implies, to overcome the ongoing separation of neurology and psychiatry, which solidified in the middle of the twentieth century. For over half a century, cognitive and behavioral neurology has been restricted mainly to dementias and behavioral aspects of neurological diseases, such as well-defined syndromes in stroke cases, whereas disorders of fundamental cognitive functions such as emotion (e.g., depression) and thought (e.g., schizophrenia) have been entitled “mental disorders” and have been investigated and treated outside the neurological milieu. Departments of psychiatry have focused on the special needs of their patients that include long hospitalizations; psychological, social, and complementary support; and adjustments of pharmaceutical and electrophysiological therapies. However, the psychiatrist does not necessarily share the neurologist’s quest to identify the underlying neuroanatomical basis of a disorder. The gap between the two disciplines becomes conspicuous in our day, as we see how the recent technologies which enable us to better investigate the neural basis of neuropsychiatric disorders have not yet led to significant breakthroughs in the comprehension, monitoring, or treatment of psychiatric diseases. This article reviews the history and development of neuropsychiatry in the occidental world, and suggests that the science of neuropsychiatry could enable the optimization of modern technologies for the diagnosis, monitoring, and treatment of behavioral, cognitive, and so-called mental disorders.

The beginning of neuropsychiatry is attributed to nineteenth century scientists in Germany and France. In France, Étienne-Jean Georget (1795–1828), a disciple of Pinel and Esquirol, emphasized the organic etiology of mental disorders, and Antoine Laurent Bayle (1799–1858) claimed that dementia and mental disorder were both aspects of the same disease.¹ In Berlin, Wilhelm Griesinger (1817–1868), professor of neurology and psychiatry who is considered by many the founding father of neuropsychiatry, stated, “Psychische Krankheiten sind Erkrankungen des Gehirns,” or “Mental illnesses are diseases of the brain.”^2,3 In his revolutionary textbook of psychiatry, Pathologie und Therapie der Psychischen Krankheiten (1845), Griesinger called for a change of attitude toward the psychiatric patient from that of sinner who should be punished and isolated, to sufferer of a biological disease who requires curing. Griesinger’s works influenced many European neuropsychiatrists, including Meyer, Meynert, Liepmann, Pick, Oppenheim, Charcot, Korsakoff, von Monakow, Babinski, Janet, Freud, Jackson, Bleuler, Kraepelin, Bonhoeffer, and Alzheimer.⁴ Kraepelin (1856–1926) and Alzheimer (1864–1915), for instance, practiced psychiatry, but hoped to discover the basis of psychiatric diseases through histological or neuropathological methods.⁵

In North America, Benjamin Rush, a renowned Philadelphian physician (1746–1813), claimed that mental illnesses “are moved by the same causes and subject to the same laws” as other diseases of the human body. But despite this assertion, in nineteenth century America, neurology was practiced in hospitals, whereas psychiatry was restricted to sanatoriums and asylums.⁵ The Boston Psychological Society, founded in 1880 by eight psychiatrists, began accepting neurologists as members a decade later, so that in 1901 its name was changed to the Boston Society of Neurology and Psychiatry. Neurologist James Jackson Putnam (1846–1918) and his colleagues at Harvard are notable for their interdisciplinary cooperation, which brought together psychologists, philosophers, neurologists, and psychiatrists.⁵ In the earlier 1900s, then, neuropsychiatry was an emerging discipline in the German- and French-speaking world, and to a certain extent in the United States.

With the rise of psychodynamics at the beginning of the twentieth century, the interest in the relationship between psychiatric disorders and the brain was gradually abandoned. Psychiatrists enthusiastically embraced the key that they were given to the human psyche, and this new “mentalistic” approach consequently detached psychiatry from neurology. It may be further speculated that neurologists, too, accepted this dichotomy and were relieved to leave the treatment of mental illness to others.⁶ It is plausible that neurologists were deterred by a combination of factors, namely patients’ characters and personalities; lack of knowledge in diagnosis, pharmacotherapy, and psychotherapy; and inexperience with cognitive and emotional aspects of neuropsychiatric disorders. In the United Kingdom, Sir Charles Symonds (1890–1978), the doyen of British neurologists, tried to oppose this separation, but his opinion was rejected by his colleagues.⁶

An influential factor on the history of neuropsychiatry was the forced migration of German-speaking clinical neuropsychiatrists and neuroscientists after the rise of Nazism and Fascism in central Europe. As detailed in a recent study by Stahnisch,⁷ of the 52,000 doctors in 1933 Germany, about 16% were of Jewish ancestry or what the Nazis defined as being Jewish. This made approximately 8,000 to 9,000 physicians when Hitler came into power. Various clinical areas of psychiatry and neurology were rejected because they were seen as representing instances of a Jewish Science. Nearly 30% of all those expulsed physicians and faculty members practiced neurology and psychiatry, and overall, more than 600 researchers and physicians in the clinical neurosciences immigrated into North America. Consequently, the relations between neurology, psychiatry, psychology, and pathology underwent a gradual readjustment, and clinical brain sciences had become a leading biomedical field in North America. Notably, many of the immigrants were influenced by a holistic neurology approach and by adjacent fields such as philosophy, psychology, and history as well as by an experimental approach. Among the prominent figures were the neurologist, psychiatrist, and psychologist Kurt Goldstein (1878–1965), who with psychiatrists and psychotherapists Fritz Perls (1893–1970) and Laura Perls (1905–1990) founded Gestalt therapy; Adhémar Gelb (1887–1936), Victor Franz (1883–1950), and Walter Riese (1890–1976), who was the director of the Neuroanatomical Institute at the Frankfurt Psychiatric Hospital. The interchange between neurology and psychiatry, humanity and experimental approach, is exemplified in figures like the neurologist and psychiatrist Karl Stern (1906–1975), changing from a neuropathologist in Europe to being a clinical psychiatrist and ardent university teacher in Canada; Robert Weil (1909–2002), the founding member of the Canadian Psychiatric Association (CPA), who implanted statistical methods in mental health research and diagnostic testing of psychopathological conditions; or the prominent Berlin neurologist Friedrich Heinrich Lewy (1885–1950) best known for the discovery of Lewy Bodies.⁷ To summarize, the effects of the process of forced-migration on modern clinical brain research and the transplantation of European concepts and methods into the North American clinical and basic neuroscience has contributed to interrelations between the clinical brain sciences of neurology, psychiatry, neuropathology, and experimental psychology, into an inter-reliant framework.

After World War II, the division between neurology and psychiatry became explicit. The Archives of Neurology and Psychiatry, first published in 1919, was separated into two journals. The American Academy of Neurology was founded in 1948 to deal with “pure” neurological issues, and separate neurology departments were established throughout the United States.^5,8 In 1965, the Residency Review Committee for Psychiatry and Neurology (RRC, now separated between neurology and psychiatry), an accrediting body separate from the American Board of Psychiatry and Neurology (ABPN), deleted psychiatric training as a mandatory experience for neurologists.⁴ At the same time, with the introduction of neuroleptics, biological psychiatry began to emerge, contributing to the separation of neurology and psychiatry into two different disciplines.^4,8

In the 1980s, attitudes once again began leaning toward a linkage of the two disciplines. At a 1985 symposium in Paris marking the 100th anniversary of the naming of Gilles-de-la-Tourette syndrome, the American delegation presented evidence in support of an organic basis for the syndrome, while many in the French academy held that the syndrome was caused primarily by a psychopathologic release of repressed tendencies.⁵ The geographic roles were now swapped, with the English speaking countries now leading the re-alliance of neurology and psychiatry. In 1989, the American Neuropsychiatric Association (the ANA, and now ANPA) was established. In the United Kingdom, neuropsychiatric services evolved at a few regional and national centers such as the National Hospital for Neurology and Neurosurgery in London, the Institute of Neurology (ION), and the Institute of Psychiatry (IOP); and the British NeuroPsychiatry Association (BNPA) was established in 1987.

In recent years, several attempts have been made to define the scope of neuropsychiatry. The suggested definitions may be divided into two main categories—minimal and maximal. The minimal approach puts neuropsychiatry in the borderland between neurology and psychiatry, and sees its subject matter as “disorders that cross the boundary between the two disciplines”⁹, as well as neurological aspects of psychiatric disorders and psychiatric aspects of neurological disorders.¹⁰ The maximal approach includes the full range of central nervous system diseases (occurring ‘above the foramen magnum’), as well as most of the psychiatric disorders, within the scope of neuropsychiatry. For example, in a paper aiming to define the curriculum for subspecialty in behavioral neurology and neuropsychiatry,¹¹ the authors defined the scope of neuropsychiatry to include “at minimum”: classical syndromes of behavioral neurology (e.g., aphasias, apraxias, agnosias); delirium; dementias, the major primary psychiatric disorders; neurological conditions with cognitive, emotional, or behavioral features, including movement disorders, stroke, epilepsy, multiple sclerosis, traumatic brain injury; and comorbid neuropsychiatric and neurological conditions. Rather than refer to specific disorders, the definition of neuropsychiatry may be generalized in adherence to scientific advancement, regarding neuropsychiatry “as that aspect of psychiatry which, like neurology, seeks to advance understanding of clinical problems through increased knowledge of brain structure and function,”⁶ or “understanding the neurological basis of psychiatric conditions.”¹⁰ However, despite developments in the pharmacological treatment of major psychiatric disorders such as psychosis and depression, biological psychiatry is still considered inferior to behavioral psychiatry. Thus, a dichotomy still exists between psychiatry and the clinical neurosciences. In the near future, major aspects of the clinical neurosciences may be reintroduced into traditional psychiatry with the application of advanced neuroimaging methods and genetic analyses as biological markers for diagnosis, monitoring, and treatment in psychiatric disorders. These are further empowered by the computational revolution of the recent years, enabling the application of sophisticated algorithms on “big-clinical-data” to enable better understanding and management of the individual patient based on the patient's own disease history, brain processes, and genetic profiles. Potential new medical treatments, such as electrical and magnetic neurostimulation, are already used in psychiatric disorders, and chemical and optical neuromodulation and gene therapy are expected in the more distant future. Computer sciences supply new algorithms and analyses methods as well as powerful interconnected devices to process the patient's information in real-time. In the field of neuro-immunology, a number of syndromes characterized by psychiatric changes have been found to result from autoimmune dysfunction, at times with autoantibodies that guide both diagnosis and treatment, demonstrating how abnormal autoimmune processes can result in profound neuropsychiatric symptoms,^12,13 further stressing the loose border between the neurological and psychiatric worlds.

In conclusion, the conceptual scopes of neuropsychiatry have varied over time. At the onset of the clinical neurosciences, neurology and psychiatry were merged. Later, as the specialties developed, the two domains went off in different directions, splitting into two separate sciences. With our current scientific understanding of the cerebral basis of psychiatric disorders, the era of the computational, data, and genomic revolutions once again merges the domains of neurology and psychiatry for a neuroscientific-based diagnosis, monitoring, and treatment of neuropsychiatric diseases.