Duke University researchers, who ran personal interviews and brain scans for a study, have become the first to link specific differences in brain structure to what is common across many types of mental illness.

More than 1,000 students on campus participated in the study that found individuals who exhibited symptoms that cross over many types of mental illness consistently exhibit differences in the cerebellum and the pons—structures traditionally known for helping us coordinate complex movements.

"Individuals with comorbidity tend to have worse outcomes in treatment, and that could be because we are not targeting the actual underlying process of what is shared among the disorders," said Adrienne Romer, clinical psychology graduate student in neuroscience and psychology at Duke University in a statement. "We hope we could eventually use these findings to identify individuals at risk for developing multiple forms of mental disorder and determine the risk factors so that we can target those earlier on.

The study, published in Molecular Psychiatry, outlines recent analyses of mental health data that shows that psychiatric symptoms are often times highly correlated. Researchers have labeled these correlations in a score called the “p-factor.”

"Higher p-factor scores indicate greater comorbidity across common forms of mental illness, and are associated with greater dysfunction, more severe illness and more hospitalizations," said Ahmad Hariri, a professor of psychology and neuroscience at Duke, in a statement. 

Participants who were involved in the study underwent mental health assessments that were used to estimate each person’s p-factor score. Then, the student’s underwent MRI, which researchers used to test correlations between the estimated p-factor score and grey matter volume, a measure of brain density, and the integrity of white matter pathways throughout the brain.

Researchers found that high p-factor scores were correlated with lower grey matter volume in the cerebellum, a region of the brain associated more with motor function and coordination than with emotion and thinking. Students with these high p-factor scores also had less integrity of white matter pathways within the pons, which include wiring that connects the cerebellum with higher order reasoning centers in the prefrontal cortex.

"This work suggests that the p-factor may very well be tapping into inadequacies or deficiencies in simply our ability to monitor information—including our own thoughts and emotions—and make sure they jive with our intentions, our expectations and the responses that we get from the world outside," Hariri said. "When that goes awry, and the extent to which that goes awry, may result in either milder forms of mental illness or more and more severe forms of mental illness.”

Benjamin Lahey, professor of epidemiology, psychiatry and behavioral neuroscience at the University of Chicago, warned that researchers may find it challenging to replicate these findings on a more diverse group, as the individuals from Duke may be healthier and have a higher intelligence than the general population.

Researchers will continue their research by repeating the study on various populations, beginning with New Zealanders who will participate in the long-term Dunedin study, and will gather more detailed MRI scans of the cerebellum, to find out more precisely what role this part of the brain plays in mental health.

"Outside of a pocket of dedicated researchers, the cerebellum is a largely neglected structure in neuropsychiatric research," Hariri said. "Cerebellum literally means 'little brain,' and we aim to give it a little more respect."