What Do Brain Scans Tell Us About PTSD?
Although researchers do not use brain scans to diagnose PTSD in the clinic, they use them to understand what happens in the PTSD brain.
There is abundant evidence for changes in the structure and function of different areas of brain involved in fear response and anxiety, regulation of emotions, cognitive processing and memory.
For example, there is consistent evidence for reduced volume in the brain region called the hippocampus, which is involved in memory and context processing. This leads to difficulties differentiating cues that resemble trauma, such as the slamming of a door, from the trauma cue itself, such as a gunshot.
What are brain scans?
A brain scan is a general term that covers a diverse group of methods for imaging the brain. In psychiatric clinical practice, brain scans are mostly used to rule out visible brain lesions that may be causing psychiatric symptoms.
However, in research we use them to learn about the pathologies of the brain in mental illness. A common method is magnetic resonance imaging (MRI) that allows us to look at the changes in the volume and structure of different areas of the brain, and integrity of the pathways connecting them.
Then there is functional MRI (fMRI). This method examines blood flow in different areas of the brain as a measure of their dynamic function, mostly in response to a task or event, such as thinking about trauma or viewing of a trauma-related image. I use fMRI in my research to look at the brain circuitry involved in how people can be instructed to learn fear and safety. Positron emission tomography, or PET, and single photon emission CT, or SPECT, are also used in looking at brain function.
At the current stage of the technology and research, psychiatrists, psychologists and neuroscientists only use these methods for researching the brain changes in mental illness, and not for making diagnoses.
In other words, researchers have to combine data from tens of people with a mental illness to determine how, on average, different areas of their brain may differ in volume or function from others.
How do we diagnose PTSD?
Like most other psychiatric conditions, PTSD is a clinical diagnosis. That means psychiatrists diagnose PTSD by the symptoms presented by the patient. Clinicians look for a constellation of symptoms for a diagnosis:
- history of exposure to trauma
- intrusive symptoms such as frequent flashbacks, nightmares, intrusive memories
- avoiding any reminder of trauma (for example, a veteran avoiding watching the movie “Saving Private Ryan”) and its memories
- hyperarousal, or being overly vigilant, having sleep disturbances, being easily startled negative thoughts or feelings
significant distress or dysfunction.
When enough number of the above criteria is met, a clinician makes a diagnosis of PTSD.
Clinicians and researchers use the above criteria for consistency in research. They want to be sure that what they call PTSD across different studies passes the threshold of a certain severity and diversity of symptoms.
However, effects of trauma may not reach the “diagnostic threshold” forPTSD, but can still be very stressing. A traumatized person who has frequent nightmares and flashbacks and avoids leaving their house out of fear, is seriously stressed even though they may not meet the required number of “negative symptoms” per the diagnostic manual. From a clinical perspective, we still address their symptoms and treat them. In other words, what matters in clinical practice is helping with the symptoms that are distressing and cause dysfunction.
Population of U.S. Suffering PTSD
PTSD is common, affecting 8% of the U.S. population, up to 30% of the combat exposed veterans, and 30%-80% of refugees and victims of torture.
This Once a Soldier blog/advocacy post was reprinted in part with permission from and can be found here.