Patients diagnosed with posttraumatic stress disorder (PTSD) can experience symptoms that include under-expression of emotions, such as numbness, as well as over-expression, such as rage outbursts. These seemingly contrasting symptoms may coexist due to rapid transitions between states of hypoarousal (an understated response to an event) and hyperarousal (an exaggerated response), according to a new Yale study.

The findings, recently published in JAMA Network Open, could inform more effective therapeutic strategies, said the researchers.

[T]he findings suggest those with PTSD go from no emotional response to a very negative emotional state quickly, whereas those who don’t have PTSD experience a much more gradual transition between the two states.

For the study, the researchers recruited more than 1,400 individuals who had experienced some type of trauma, such as witnessing or experiencing a violent act or car crash. The participants then completed a PTSD checklist, a questionnaire similar to the one used to diagnose PTSD in clinical settings; those who met the criteria for diagnosis were considered probable PTSD participants and their study outcomes were compared to the trauma-exposed individuals who did not meet the criteria for PTSD.

To evaluate the participants’ emotional states, the researchers showed them a series of images that ranged from neutral (for example, a person holding a cigarette), to moderately negative (the slightly bloodied face of a boxer), to very negative (a severely injured person) and asked them to rate how pleasant or unpleasant they found the images to be.

“We found that the probable PTSD group transitioned much more quickly from a neutral to a negative emotional state, based on how they rated the images they saw,” said lead study author Nachshon Korem, an associate research scientist in the lab of Ilan Harpaz-Rotem, professor of psychiatry at Yale School of Medicine and senior author of the study.

[T]he researchers propose that with more severe emotional numbing comes a higher threshold for emotional reactivity

Essentially, the findings suggest those with PTSD go from no emotional response to a very negative emotional state quickly, whereas those who don’t have PTSD experience a much more gradual transition between the two states.

Additionally, the researchers found that those who had the highest scores for symptoms related to emotional numbing on the PTSD checklist (reporting they were more bothered by loss of interest in activities they used to enjoy, feeling distant or cut off from other people, or trouble experiencing positive feelings) had the most rapid transitions between the two states.

Based on the findings and those of other studies, the researchers propose that with more severe emotional numbing comes a higher threshold for emotional reactivity.

“When a healthy person is exposed to something slightly aversive, they may notice it is uncomfortable to them and note they should pay attention to it, but it likely won’t trigger emotion or a physiological response in the body,” said Korem. “At a certain point though they’ll reach their threshold, they will start to have an emotional response, and they’ll employ some sort of behavioral technique to regulate that response.”

For example, someone who starts to react to a scary movie may tell themselves it’s not real or turn the movie off.

“But what happens in people diagnosed with PTSD, their bodies start to secrete chemicals in response to even mild stimuli though they may not cognitively realize something is wrong,” said Korem. “Once the stimuli become more intense, they may notice it, but by that point their body’s defense mechanisms are already at maximum capacity and there’s no window for them to use techniques to handle the situation. That’s when you get the emotion overshoot.”

These findings could inform treatment strategies, particularly approaches focused on emotion regulation that might help individuals manage or prevent the abrupt escalation in reactivity, researchers said.

Going forward, the researchers aim to better understand the link between emotional and physiological responses to stimuli in people with PTSD.