Today in the Baliwick Express, Guernsey addition, an article about masks triggering PTSD for Afghanistan war veterans. Many terrorists cover their faces so being bombarded by angry mask wearers who are hiding their identity and emotion under their mask can be very triggering of war time flashbacks - to make matters worse, these veterans are often hard of hearing from bomb blasts and can’t read the mask-wearers lips or hear their muffled voices.
PTSD can be triggered simply by being forced to do something you don't want to do.
It often relates to surpressed trauma memories from early childhood, trauma in adult life can trigger the early fixed emotional memory without knowing or rememering what caused the original trauma.
This is why Psychedelic therapies are showing great promise in treatment for PTSD (now starting to be defined as complex PTSD) as the drugs can allow the patient to access the original memories and process them correctly with the benefit of mature adult experience and context.
There's a good doc on Netflix atm covering the first Psychedelic drug trial for treatment resistant depression in London, the parallels with cPTSD are obvious.