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What is causing Havana Syndrome, the mysterious illness that has struck hundreds of US diplomats? © Getty Images

What is causing Havana Syndrome, the mysterious illness that has struck hundreds of US diplomats?

Published: 15th December, 2021 at 16:25
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Commentators have blamed everything from noisy insects to sonic weapons, but the condition could be psychological in nature.

In December 2021, a former FBI agent previously posted to Guangzhou in China began legal proceedings against the US government. The agent claimed the US Secretary of State and the State department hadn't taken the situation seriously enough when, a few years earlier in Guangzhou, the agent and his family had begun experiencing sudden headaches, dizziness, nosebleeds, memory loss and nausea.


It was just the latest development in a saga that first began to unfold in 2016 when dozens of US agents and staff based at the US embassy in Cuba began describing a similar range of neurological symptoms, in many cases accompanied by an eerie or ear-splitting sound and facial pain.

Depending on who you ask, so-called 'Havana syndrome' – which by now has reportedly affected more than 200 US staff based not only in Cuba and China, but also Germany, Austria, Russia and Serbia (there was also a recent suspected case in Washington) – is caused by a malicious sonic or microwave-based weapon developed by the Russians, or it is a textbook instance of mass psychogenic illness.

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The Russians deny having or using an acoustic weapon that can target the brain. However, in 2020, the US National Academies of Sciences, Engineering, and Medicine published a detailed scientific report in which they concluded "many of the distinctive and acute signs, symptoms, and observations" described by US employees are "consistent with the effects of directed, pulsed radio frequency energy". And in November 2021, the FBI finally admitted to the media that it has issued a formal warning to its staff about what it calls "Anomalous Health Incidents".

There are reasons for being sceptical about the weapon-based theory, though. Security experts have commented that it's unlikely Russia would have been able to develop some as-yet-unidentified technology without the West finding out about it. Neurological experts have pointed out that it is implausible that a sonic device could selectively target the brain.

The mating call of the cricket Anurogryllus celerinictus has been proposed as the cause of Havana Syndrome © Brandon Woo/
The mating call of the cricket Anurogryllus celerinictus has been proposed as the cause of Havana Syndrome © Brandon Woo/

Meanwhile, recordings reportedly taken of the intense sounds heard in Cuba (and blamed for the symptoms) have been identified as most likely being the mating call of a Caribbean cricket by researchers at the University of California, Berkley. And 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.

Worth noting is that the initiator of a psychogenic outbreak could have a physical illness, but to meet the criteria for mass psychogenic illness, those subsequently affected must not have been exposed to the physical cause, but only to the idea of the symptoms.

At the heart of this phenomenon is the 'nocebo effect', which is the harmful reverse of the 'placebo effect' – in this case, the mere belief that something is harmful can provoke real unpleasant symptoms, just as positive beliefs about a placebo pill can induce real medical benefits. That word 'real' is important. Just because the causes of a syndrome are psychological does not mean the suffering and symptoms are not real.

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There are countless confirmed cases of mass psychogenic illness in the medical literature. Here is just one: imagine being at school and suddenly a rising number of your classmates report sensing a strange smell and coming down with intense nausea. As fears grow, you too begin to feel discomfort in your stomach and before you know it, you too are sick.

It is hard to believe it is all in the mind and that there is not some kind of a chemical spill or gas leak. Yet this is exactly what happened at a South Yorkshire school in 2006 when more than 30 pupils and a teaching assistant were suddenly taken ill. No leak was ever found and of those pupils rushed to hospital, all were discharged within a few hours.

It is not currently possible to know for sure whether Havana Syndrome is an instance of mass psychogenic illness, but it does fit some or all of the criteria. Many of the affected agents have been operating in stressful, dangerous environments. They have been in close contact with each other, exposed to the idea of the symptoms and the dread that they too might be affected. In the absence of any apparent physical explanation, and with the sonic weapon being purely theoretical and unproven at this point, then a psychological cause seems plausible.



Dr Christian Jarrett is a cognitive neuroscientist, science writer and author. He is the Deputy Editor of Psyche, the sister magazine to Aeon that illuminates the human condition through psychology, philosophy and the arts. Jarrett also created the British Psychological Society's Research Digest blog and was the first ever staff journalist on the Society's magazine, The Psychologist. He is author of Great Myths of The Brain and Be Who You Want: Unlocking the Science of Personality Change.


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