One Neural Network May Link Various Major Psychiatric Illnesses

The findings suggest that reduced gray matter is not the cause of psychiatric illness, although it is found in regions of the brain associated with it.

Investigators identified a specific transdiagnostic network common among patients with psychiatric illness, according to findings published in Nature Human Behavior. Nearly 85% of studies conducted assessing this transdiagnostic network show it presents with reduced gray matter, according to the study authors. Based on this knowledge, less gray matter was thought to have a causal relationship with psychiatric illnesses such as depression and schizophrenia.

“Traditionally, neurology and psychiatry have different diagnostic strategies,” said coauthor Joseph J. Taylor, MD, PhD, a medical director of Transcranial Magnetic Stimulation at the Brigham’s Center for Brain Circuit Therapeutics, and an associate psychiatrist in the hospital’s Department of Psychiatry, in a press release. “Neurology asks: ‘Where is the lesion?’ and psychiatry asks: ‘What are the symptoms?’ We now have tools to explore the ‘where’ question for psychiatry disorders.”

Nearly 1 in 5 US adults are diagnosed with a psychiatric illness, approximately 50% of whom also meet the criteria for a second psychiatric illness. The anterior cingulate and insula are brain regions known to be associated with psychiatric illnesses. In a recent study, investigators at Brigham and Women’s Hospital, part of the Mass General Brigham health care system, hypothesized that many psychiatric illnesses are caused by a neurobiological source.

Comparing the structural brain data of 15,000 individuals without diagnosed psychiatric illnesses with that of patients diagnosed with a psychiatric illness, such as schizophrenia, bipolar disorder, depression, addiction, obsessive-compulsive disorder, or anxiety, the investigators examined differences in patients’ brain network using 4 pre-existing neurological and psychiatric datasets.

Investigators then used a human connectome to test if the presence of gray matter mapped a common brain transdiagnostic network in different subsets of psychiatrically ill patients. In this analysis, they found that the transdiagnostic network was linked to psychiatric disorders .

In a secondary analysis, the team studied data of the brain networks of all psychiatric disorders at the same time. The results were supported that of the first analysis, demonstrating a link between the network and multiple psychiatric illnesses.

A separate analysis then looked at the brain scans of 194 veterans with psychiatric diagnoses—some of whom also had a penetrating head trauma. Based on this assessment, the investigators concluded that lesion-induced damage to the transdiagnostic network also correlated with an increased likelihood of multiple psychiatric illnesses as well.

The evidence from these studies have now led investigators to believe that the posterior parietal cortex may be the node linked to the transdiagnostic network. Certain investigators plan to use Transcranial Magnetic Stimulation (TMS) to change the network and target the posterior parietal region. The team identified numerous follow-up studies on the horizon based on the promising results of this study.

“Psychiatric disorders are brain disorders, and now we're just beginning to have the tools to study and modulate their underlying circuitry,” said Taylor in the press release. “There may be more in common across these disorders than we originally thought.”

Reference

Brigham and Women’s Hospital. Common Brain Network for Psychiatric Illness Discovered. News Release. January 12, 2023. Accessed January 19, 2023. https://www.brighamandwomens.org/

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