"Essentially, PTSD is based in the human fight-or-flight response, which has remained partially active after a trauma event though the causal event is no longer present," said Terence Watts, a London-based psychotherapist, author and founder of The BWRT Institute.
"Even after the event has passed, the memory of it remains vividly lifelike and can trigger strong emotional responses, mainly fear and/or anger," Watts said.
The UK National Health Service defines PTSD as an anxiety disorder caused by very stressful, frightening or distressing events, according to Simon Davies, a walking therapist at Living Well UK, providing free mental health services in Birmingham and Solihull, U.K. While the symptoms can vary between individuals, they are generally characterized by:
- Avoidance of situations and experiences linked to the traumatic event
- Feeling extremely anxious and on edge nearly all of the time and/or feeling emotionally numb or detached
- Re-experiencing the traumatic event(s) in flashbacks, nightmares or physical sensations
"The exact mechanisms that lead to some people developing PTSD are not fully understood, but there are theories that are helpful in understanding the condition," Davies said.
When going through an extremely distressing or frightening experience, he noted, our brains and bodies engage in a survival mechanism known as the fight-or-flight response.
This floods the brain and body with natural stress hormones such as adrenaline to deal with a perceived threat, increasing our heart rate, moving blood to our muscles, and temporarily reducing activity in areas of the brain associated with memory and emotional processing.
"While all of these changes can help us deal with a threatening situation in the short term, for some people, these changes remain after the event and are seen in the symptoms described above," Davies said.
Theories suggest this may either be the brain and body's way of protecting us from similar events happening again or because we weren't supported enough to fully process what happened in the first place.