The Physical Alterations of PTSD: Shrinking the Brain's Cerebellum

The cerebellum is a significant part of the brain, possessing half of the brain's neurons although it is quite small. Its size is the root of its nickname, the tiny brain. Current research has linked a decreased cerebellum size with PTSD, providing a new perspective in understanding the neurological basis of the disorder, as well as potential treatment methods. Image Credit: Dan Vahaba, Duke University.

The cerebellum of people suffering from PTSD is generally 2% smaller than that of unaffected individuals, particularly in areas related to emotion and memory.

A Duke-led brain imaging study establishes that adults diagnosed with posttraumatic stress disorder (PTSD) tend to have smaller cerebellums.

Although the cerebellum is renowned for its importance in coordinating movements and ensuring balance, it also greatly influences emotion and memory, both of which are affected by PTSD. However, it remains uncertain as to whether a smaller cerebellum creates a predisposition towards PTSD or whether the development of PTSD results in shrinkage of this part of the brain.

Ashley Huggins, Ph.D., the primary author of the study, has pinpointed the chief differences to be within the posterior lobe and the vermis. Her hope is that these findings motivate others to recognize the value of the cerebellum as a crucial medical target for those with PTSD.

Huggins believes that understanding the implicated areas can guide interventions such as brain stimulation, potentially leading to better treatment outcomes.

Published in the journal Molecular Psychiatry on January 10, these discoveries have spurred Huggins and her team to investigate the causality—whether the susceptibility to PTSD stems from a smaller cerebellum or if PTSD-induced trauma causes the shrinkage of the cerebellum.

PTSD is a mental health disorder resulting from experiencing or witnessing a traumatic event. While a majority of those who go through such experiences escape the disorder, around 6% of adults develop PTSD, characterized by escalated fear and recurring memories of the traumatic incident.

In addition to the cerebellum, PTSD also involves several other parts of the brain, such as the amygdala which regulates fear, and the hippocampus that processes memories.

The cerebellum, or "little brain", although not commonly associated with PTSD, plays a crucial role in the disorder. Despite its small size, it houses over half of the brain's neurons, and is densely packed with cells responsible for complex functions beyond balance and movement.

Researchers have noticed changes in the size of the cerebellum in PTSD patients. Limitations in the research were addressed in this study by Dr. Morey from Duke and over 40 other research groups, who shared their brain imaging scans to broadly study PTSD.

The collective data, comprising images from 4,215 adult MRI scans, revealed that about a third of the subjects had been diagnosed with PTSD. This data demonstrated that patients with PTSD typically had cerebellums that were 2% smaller in size.

Focusing on particular areas within the cerebellum that affect emotion and memory, Huggins identified similar cerebellar reductions in individuals with PTSD. It was also determined that the severity of PTSD in an individual was proportionate to the size of their cerebellum.

“Focusing purely on a yes-or-no categorical diagnosis doesn’t always give us the clearest picture,” Huggins said. “When we looked at PTSD severity, people who had more severe forms of the disorder had an even smaller cerebellar volume.”

The results are an important first step in looking at how and where PTSD affects the brain.

There are more than 600,000 combinations of symptoms that can lead to a PTSD diagnosis, Huggins explained. Figuring out if different PTSD symptom combinations have different impacts on the brain will also be important to keep in mind.

For now, though, Huggins hopes this work helps others recognize the cerebellum as an important driver of complex behavior and processes beyond gait and balance, as well as a potential target for new and current treatments for people with PTSD.

“While there are good treatments that work for people with PTSD, we know they don’t work for everyone,” Huggins said. “If we can better understand what’s going on in the brain, then we can try to incorporate that information to come up with more effective treatments that are longer lasting and work for more people.”