Yes placebo effect but in the other direction. A person taking a sugar pill can report that they feel better, just as a person thinking something bad happened when it didn’t can report negative effects from this. Common human phenomenon.

If John is at a dinner with 10 friends who want to play a prank....after dinner they all fake being severely ill and food poisoned...it’s very probable John will talk himself into feeling sick with even physiological changes resulting etc- the brain is powerful.

Now in this case, if you are given a clip of a sound (such as insect noises) and told before your trip to the embassy to be VERY careful and that something bad happens with that sound or other loud noise, which could lead to brain damage etc.....guess what’s going to happen when you then hear the sound.

It is noteworthy the symptoms seem to be more vague (brain fog, difficultly concentrating, headache) that can occur with all kinds of illnesses, including ones of psychogenic origin, rather than say some neurological damage such as paralysis, uncontrolled movement etc. It is reminiscent of the symptoms of fibromyalgia, a somewhat notorious dubious diagnosis.

I’m skeptical and leaning toward psychogenic/mass hysteria , but who knows for sure.