Neural circuits approach could change psychiatry for better

The Diagnostic and Statistical Manual has been a revolutionary development in psychiatric nosology. Before the DSM, it was not clear if what was considered major depression in one country was the same as major depression in another country. Even within the United States, it was not clear if a certain psychiatric diagnosis was the same across regions or state lines. The DSM has allowed everyone in psychiatry to speak the same language. This is critical, as now psychiatric diagnoses are reliable. Reliable, however, doesn’t necessarily mean valid.

Validity refers to how close the diagnosis is to biological reality. In psychiatry, then, it refers to how close the diagnosis matches what is actually going on in the organ at hand – in the case of our profession, the brain.

Our knowledge base in neuroscience has been growing immensely. However, despite many, many neuroscience studies relevant to psychiatry, translating this knowledge to clinical practice has been difficult. There is almost a schism in clinical psychiatry: journals are full of neuroscience studies, replete with pictures of the brain, but actual clinical practice is more likely to involve running through a list of symptoms to make a diagnosis – the DSM approach.

Although the DSM approach allows us all to diagnose syndromes the same way and ensures that we are talking about the same entity, there is often no clear-cut correlation with the neuroscience research base. This presents a problem. Is there a better way?

Thinking of psychiatric symptoms in terms of neural circuits, in the same way we consider neurological symptoms to be correlated with damage to neural circuits, might be a better approach. If a patient has hemiparesis, neurologists are trained to think about where the lesion is. The lesion could be in the corticospinal tract if it is an upper motor neuron lesion, or it could be tied to more peripheral damage (at the spinal nerve level or at the neuromuscular junction, for example). Similar thinking could be done for psychiatric symptoms.

The argument could be made that we simply do not have knowledge about brain circuits instantiating psychiatric symptoms, as we do for neurological symptoms, like hemiparesis. Here, it is useful to look at what neuropsychiatry can teach us. Neuropsychiatry and behavioral neurology, which have joined forces in terms of training (there is a common fellowship and common exam through the United Council for Neurologic Subspecialties), have a long history of discovering the neural bases for mood, behavioral, and cognitive symptoms. Based on studies of patients with neurological disorders, such as stroke and epilepsy, areas of the brain necessary for mood regulation, behavioral regulation and attention, memory and executive function, among other functions, have been clarified.

Psychiatric symptoms, such as depression, anxiety, or mania, can occur with damage to particular neural circuits. This is not news from a neuropsychiatric perspective, but this idea has not been transmitted very well to general psychiatrists. General psychiatrists might attribute mood, behavioral, and cognitive symptoms in their patients to genetic vulnerability, combined with environmental factors, like a traumatic childhood. Neuropsychiatrists might attribute these same symptoms in their patients to stroke, seizure, traumatic brain injury, or brain tumor. Whatever the immediate cause, however, when particular circuits are damaged, certain psychiatric symptoms will consistently result.

It is my belief that this circuit-based way of thinking – which I and Dr. Vani Rao describe in a new book, “The Traumatized Brain” – will lead to a widespread change in psychiatry. This new paradigm could lead to renewed rigorousness and common cause with the rest of the medical community. After all, not just neurologists, but most physicians, are trained to think in terms of pathophysiology, rather than in terms of a list of symptoms grouped together arbitrarily into syndromes.

Thinking about symptoms (impulsivity, mania, agitation, depression, psychosis, etc.) rather than syndromes (major depressive disorder, schizophrenia, bipolar disorder, etc.) allows closer mapping to underlying neural circuits. This, in turn, may lead to more judicious use of medications. Our medications, after all, treat symptoms rather than the underlying putative disorder. This clinical approach also is in line with the National Institute of Mental Health’s new Research Domain Criteria for research studies.

The future of psychiatry is in learning from the rest of medicine in terms of clinical thinking, in particular from neurology, and even more specifically, from neuropsychiatry and behavioral neurology.

Dr. Vaishnavi is the director of the neuropsychiatric clinic at Carolina Partners in Raleigh, N.C., and a neuropsychiatrist at the Preston Robert Tisch Brain Tumor Center at Duke University in Durham, N.C. He is coauthor, with Dr. Rao, of “The Traumatized Brain: A Guide to Understanding Mood, Memory, and Behavior after Brain Injury” (Baltimore: Johns Hopkins University Press, 2015).