Why Are Some People More Vulnerable to PTSD than others?

Why Are Some People More Vulnerable to PTSD than others?

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Few mental health disorders increase your vulnerability to addiction as much as post-traumatic stress disorder. PTSD comprises a number of symptoms, each of which, individually, might make someone use drugs or alcohol to cope. These include flashbacks or nightmares about the traumatic event, negative thinking about oneself, other people, or the world, hopelessness, emotional numbness, feeling detached, avoiding thoughts or things associated with the trauma, irritability, guilt, trouble sleeping, and being easily startled, among others. One study estimates that as many as half of people seeking help for a substance use disorder also meet the criteria for PTSD, which is about five times higher than in the general population. 

One curious thing about PTSD is that most people who experience a traumatic event don’t develop the condition. Since PTSD is a way of adapting to a life-threatening situation, it would make sense if it were more common. However, most people who survive a traumatic event may experience symptoms for a few weeks and then those symptoms resolve on their own. About 60 percent of men and 50 percent of women experience some kind of trauma in their lifetime but only about four percent of men and 10 percent of women ever develop PTSD. Why do some people develop PTSD after trauma while others don’t?

Intensity of trauma

Perhaps the most relevant factor in whether someone develops PTSD is the intensity of the trauma. This makes sense intuitively. For example, it’s bad to be seriously injured in a car accident but it’s even worse to be seriously injured and have several immediate family members die in the same car accident. Either scenario may lead to PTSD but the risk is greater in the latter. 

One study of Vietnam War veterans found that the severity of trauma was likely the most important factor. Out of the service members who were involved in potentially traumatic combat, 31.6 percent developed PTSD. However, of the service members who experienced the most traumatic combat, the number who developed PTSD rose to 70 percent. This shows a clear dose-response relationship between the severity of trauma and PTSD but it also shows that about 30 percent of soldiers were exposed to severe trauma but didn’t develop PTSD. This study also found that part of what made an experience traumatic was if soldiers were involved with harming civilians. If a combat veteran met three criteria–exposure to combat, had a pre-existing mental health issue and was involved in harming civilians, there was a 97 percent chance he developed PTSD. 

Social support

Social support is one major factor that can reduce the risk of developing PTSD following a traumatic event. On the other hand, less social support can significantly increase your risk. One study of combat veterans found that less social support correlated with not only higher rates of PTSD but also higher rates of substance use disorders. It appears different kinds of social support may affect your PTSD risk in different ways. For example, positive social interactions may make the symptoms of PTSD less severe, while feeling emotionally supported may make treatment more effective. Social support is also a key factor in recovering from a substance use disorder. It helps reduce stress, gives you a forum to discuss your feelings, and increases your sense of accountability. 

Pre-existing mental health issues

Several studies have identified pre-existing mental health issues as a major risk factor in developing PTSD. The above study of Vietnam War veterans found that service members who had been abused as children or who had been diagnosed with mental health issues other than PTSD were more likely to develop PTSD following combat. 

Other studies have suggested that characteristics that make people vulnerable to other mental health issues also make them vulnerable to PTSD. One brain imaging study of people with PTSD found they typically have features similar to the brains of people with depression and anxiety disorders. Their hippocampus and anterior cingulate cortex shrink, while the prefrontal cortex becomes less active and the amygdala more active. On the other hand, people who experience trauma but don’t develop PTSD show more activity in their prefrontal cortex, suggesting their brains have a greater structural ability to regulate their emotions.

Scientists have also identified genetic factors that influence hormonal responses to stress. One gene variant was found to make people more vulnerable to PTSD following trauma while another gene variant essentially mutes threat-sensitive parts of the brain when exposed to stress, which protects the carrier from PTSD. 

Age of trauma

In the study of Vietnam War combat veterans, the age at which soldiers experienced trauma also proved to be a significant factor in developing PTSD. Soldiers who were under the age of 25 when they entered the war were seven times more likely to develop PTSD. The human brain isn’t fully mature until age 25, so it makes sense that younger soldiers would be physiologically less capable of emotional regulation than their older peers. The younger soldiers may also have been composed of more draftees who did not choose to be there and felt less control over their situation. Either way, adults over the age of 25 typically have more life experience, more emotional maturity, and more resources for dealing with adversity, all of which can mitigate their risk of developing PTSD.

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