> Top of the list: train drivers.
I rather suspect front-line in Trust and Safety at any major social media outfit is up there, too.
Anyway, this is all arse backwards: You start off with a diagnosis of PTSD based on symptoms and try to work out causation, through diagnosis. You don't start off with: "I worked on a helpdesk for attorneys and therefore I have PTSD".
1 - https://www.talkspace.com/mental-health/conditions/articles/...
It is certainly a good skill to be able to defuse situations where the customer is angry and ranting, but there is hopefully no personal or intimate connection with said customers, and that's really the key to effective emotional abuse. Likewise, the worker is hopefully not enduring emotional abuse from coworkers or management in the course of their jobs, although this is also a possible thing.