PTSD and TBI have many overlapping symptoms. Now, a brain study of 20,000 people has found how to tell the two conditions apart.

In 2008, Capt. Patrick Caffrey of the 2nd Battalion, 7th Marines’ Combat Engineer Platoon was deployed in Afghanistan.

The combat engineer’s goal was to detect and remove mines, improvised explosive devices (IEDs), and other hazards from roads, clearing the way for troops and supplies to move through.

By the time Caffrey left Afghanistan, he had survived three explosive blasts that caused concussions.

These weren’t the first concussions in his life. He’d already had five or six such head injuries from playing sports and from other incidents.

Still, when he first got home, he felt fine. Not just fine, but fortunate that he’d survived Afghanistan unscathed.

Or so he thought.

Over the weeks and months following his return, Caffrey began to deteriorate. He began experiencing headaches and difficulty sleeping, as well as problems concentrating, focusing, and remembering. He had frequent angry outbursts, which he’d never experienced before.

“I was rude and nasty to people, and the worst part was that I didn’t really know just how much I had changed,” said Caffrey.

But when Caffrey sought medical help, his diagnosis was unclear. A history of surviving explosive attacks, coupled with his symptoms, pointed to two different possible conditions: traumatic brain injury (TBI) and post-traumatic stress disorder (PTSD).

So which was it?

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A new study published in PLOS One has found a way to tell TBI and PTSD apart by using brain scans.

The researchers gathered more than 20,000 people with TBI, PTSD, both conditions, or neither. They scanned participants using single-photon emission computer tomography (SPECT), an imaging technique that can measure blood flow to highly specific regions of the brain.

In a smaller group with about 100 patients of each type, they also strictly controlled for demographics and co-occurring conditions.

Although PTSD and TBI can have similar symptoms, in a brain scan, they look nothing alike, the researchers found.

Patients with TBI showed decreased activity in the prefrontal cortex, temporal lobes, and cerebellum. These brain regions govern self-control of mood and behavior, memory formation, and coordinated movement.

Meanwhile, patients with PTSD showed increased activity in the limbic system, basal ganglia, prefrontal cortex, cerebellum, and temporal, occipital, and parietal lobes. Brain regions that are involved in fear processing and emotional regulation, sensory processing, and integration of information are also affected.

Using a computer-driven analysis, in the smaller controlled group, the scientists were able to determine who had PTSD or TBI with 100 percent accuracy. Visual readings performed by humans were only 89 percent accurate, stressing the need to have such analysis performed by computers. In the larger group, accuracy did not exceed 82 percent, even with computer analysis.

“Diagnosis and treatment for PTSD and TBI [are] often based on symptom clusters, and difficulties in differentiating between these brain disorders often arise due to the symptom overlap,” said Daniel Amen, primary investigator on the study, in an interview with Healthline. “Functional neuroimaging with SPECT may hold the key to differentiating these disorders effectively, eliminating the reliance on self-report data, diagnosis based on symptom clusters, and challenges to diagnosis.”

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Capt. Caffrey eventually found his way to Amen’s clinic, where a brain scan revealed that he was living with both PTSD and TBI.

“Boy, did I underestimate the value of actually looking at the brain when you have a brain problem,” Caffrey said.

With the problem uncovered, his doctors were able to tailor his treatment.

“I felt a dramatic difference right away,” Caffrey added. “I felt more mentally sharp and focused than ever.”

When it comes to treating TBI and PTSD, it’s important to be able to tell the two apart. The treatments for one can be harmful for people with the other.

For example, the tranquilizers (benzodiazepines) that people with PTSD use to soothe an overactive brain could pack a dangerous double-punch to the already-underactive TBI brain.

Meanwhile, the regular therapies required to treat TBI could be triggering for someone with PTSD.

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Since 2000, more than 300,000 veterans have been diagnosed with TBI and more than 125,000 with PTSD — with no small amount of overlap among them. One study found that 73 percent of veterans with TBI also had PTSD.

In 2008, the Rand Corporation estimated that the costs for providing adequate care for these patients would run into the billions.

Among U.S. civilians, about 3.5 percent of adults experience PTSD — that’s about 8.5 million people. In 2010 alone, there were about 2.3 million emergency department visits for suspected TBI.

Amen cautioned in his paper that seemingly mild head impacts that happen during sports can cumulate over a lifetime into repetitive TBI with long-term symptoms.

Amen hopes his work will lead to diagnosis of PTSD and TBI based off biomarkers like the SPECT analysis, rather than symptom-based diagnosis.

“The results of this work offers help to vulnerable populations who suffer from PTSD and TBI — such as veterans — demonstrating that functional neuroimaging offers targeted care and the potential for improved outcomes,” he said.