The company relies on its two billion users to report inappropriate content. The moderators then employ the hundreds of rules Facebook has developed to determine if the content violates its policies.

“We recognize that this work can often be difficult,” Bertie Thomson, the director of corporate communications at Facebook, said in a statement. “That is why we take the support of our content moderators incredibly seriously, starting with their training, the benefits they receive, and ensuring that every person reviewing Facebook content is offered psychological support and wellness resources.”

Ms. Scola is urging Facebook to establish a fund to create a testing and treatment program through which current and former content moderators — including moderators employed by a third party — can receive medical testing and monitoring including psychiatric treatment. She is also asking that her legal fees be paid by Facebook.

Lawyers for Ms. Scola said their client was not currently giving interviews.

“What can cause PTSD has been the subject of countless articles and speculation long before it was an official diagnosis,” said Dr. Elspeth Cameron Ritchie, a psychiatrist and retired Army colonel who was formerly a senior Pentagon adviser on mental health issues. “In the vast majority of people, just seeing violent images is not enough, but in some people it could be.”

“People who operate drones and watch it blow things up suffer from PTSD even though they are not in the same room,” she added. “I’m not saying it could not happen, but we don’t see it very much.”