Brand new article about the 'syndrome', short and remarkably to the point, as to be expected when the author, Dr Christian Jarrett, is a cognitive neuroscientist and science writer:
... in 2018, a group of researchers at the University of Pennsylvania reported that the results of brain scans they’d performed on 21 former US Cuba-based staff who’d experienced the neurological symptoms showed no significant abnormalities.
When physical symptoms are experienced in the absence of any identifiable physical cause, such as a virus – and especially when the symptoms show signs of contagiousness, first appearing in one person and then appearing in others with whom they are in close contact – then one plausible explanation is mass psychogenic illness. This means the ultimate cause of the illness is people’s beliefs, which then ‘infect’ others, potentially leading to a mass outbreak. Some experts argue controversially that this is the most likely cause of Havana Syndrome.
Mass psychogenic illness has a few key components. The first is that a set of similar health symptoms emerges among a group of people who are in close contact; the second is that it often occurs in a context of intense stress or anxiety; and finally, to be confirmed as psychogenic, there must be an absence of any known ongoing organic cause, such as a virus, bacteria, poison or cutting-edge sonic weaponry.
What is causing Havana Syndrome, the mysterious illness that has struck hundreds of US diplomats? (BBC Science Focus, Dec 14, 2021)