Traumatic Stress Associated With Smaller Brain Region

According to new findings from a Duke-led brain imaging study, adults with posttraumatic stress disorder (PTSD) have smaller cerebellums.

The cerebellum, a region of the brain known for assisting with movement and balance, can influence mood and memory, both of which are affected by PTSD. What is unknown is whether a smaller cerebellum predisposes a person to PTSD or whether PTSD causes the brain region to shrink.

“The differences were largely within the posterior lobe, where a lot of the more cognitive functions attributed to the cerebellum seem to localize, as well as the vermis, which is linked to a lot of emotional processing functions,” said Ashley Huggins, Ph.D., the lead author of the report and a postdoctoral researcher at Duke in psychiatrist Raj Morey’s lab.

Huggins, who is now an assistant professor of psychology at the University of Arizona, thinks that his findings may persuade others to explore the cerebellum as a crucial treatment target for people suffering from PTSD.

“If we know what areas are implicated, then we can start to focus interventions like brain stimulation on the cerebellum and potentially improve treatment outcomes,” he said.

The findings, published on January 10 in the journal Molecular Psychiatry, have inspired Huggins and her colleagues to investigate which comes first: a smaller cerebellum, which may render people more prone to PTSD, or trauma-induced PTSD, which causes cerebellum shrinkage.

Traumatic Stress Disorder and the “Little Brain”

PTSD is a mental health disorder caused by watching or experiencing a traumatic incident, such as a vehicle accident, sexual abuse, or military warfare.

Though most people who go through a terrible experience are immune to the illness, approximately 6% of adults get PTSD, which is characterized by increased fear and repeating the horrific incident.

Several brain regions have been identified as being linked with PTSD, including the almond-shaped amygdala, which regulates fear, and the hippocampus, which is a vital hub for processing memories and routing them throughout the brain.

In contrast, the cerebellum (Latin for “little brain”) has gotten less attention for its function in PTSD.

The cerebellum, a grapefruit-sized lump of cells that appears to have been slapped beneath the back of the brain as an afterthought, is most known for its function in managing balance and choreographing complicated movements such as walking or dancing. However, there is a lot more to it than that.

“It’s a really complex area,” Huggins explained. “If you look at how densely populated with neurons it is relative to the rest of the brain, it’s not that surprising that it does a lot more than balance and movement.”

Dense is probably an understatement. The cerebellum accounts for only 10% of total brain volume but contains more than half of the brain’s 86 billion nerve cells.

Researchers recently discovered variations in the size of the tightly packed cerebellum in PTSD patients. Most of that research, however, is constrained by a tiny dataset (fewer than 100 participants), broad anatomical boundaries, or a singular emphasis on specific patient populations, such as veterans or sexual assault victims suffering from PTSD.

Subtle and Consistent Savings

Dr. Morey of Duke University, along with over 40 other research groups participating in a wider data-sharing program, combined their brain imaging scans to study PTSD as extensively and generically as possible.

The group received images from 4,215 adult MRI scans, almost one-third of whom had been diagnosed with PTSD.

“I spent a lot of time looking at cerebellums,” Huggins admitted.

Huggins manually spot-checked every image to ensure the boundaries drawn around the cerebellum and its various subregions were precise, despite using automated technologies to analyze the thousands of brain scans.

The end outcome of this meticulous research was a rather straightforward and consistent finding: PTSD patients had cerebellums that were around 2% smaller.

Huggins discovered similar cerebellar decreases in persons with PTSD when she focused on specific parts of the cerebellum that regulate emotion and memory.

Huggins also discovered that the smaller a person’s cerebellum was, the worse their PTSD was.

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

More Treatment and Research on the Cerebellum

The findings are an essential first step in determining how and where PTSD affects the brain.

Huggins noted that there are over 600,000 different combinations of symptoms that might lead to a PTSD diagnosis. It will also be vital to consider whether different PTSD symptom combinations have distinct effects on the brain.

Huggins believes that his research will help others understand the cerebellum as an essential driver of complex behavior and processes beyond gait and balance, as well as a possible target for novel and existing treatments for those suffering from PTSD.

“While there are good treatments that work for people with PTSD, we know they don’t work for everyone,” he 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.”

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