I have not written before about Havana Syndrome, mostly because I have not been able to come to any strong conclusions about it. In 2016 there was a cluster of strange neurological symptoms among people working at the US Embassy in Havana, Cuba. They would suddenly experience headaches, ringing in the ears, vertigo, blurry vision, nausea, and cognitive symptoms. Some reported loud whistles, buzzing or grinding noise, usually at night while they were in bed. Perhaps most significantly, some people who reported these symptoms claim that there was a specific location sensitivity – the symptoms would stop if they left the room they were in and resume if they returned to that room.

These reports lead to what is popularly called “Havana Syndrome”, and the US government calls “anomalous health incidents” (AHIs). Eventually diplomats in other countries also reported similar AHIs. Havana Syndrome, however, remains a mystery. In trying to understand the phenomenon I see two reasonable narratives or hypotheses that can be invoked to make sense of all the data we have. I don’t think we have enough information to definitely reject either narrative, and each has its advocates.

One narrative is that Havana Syndrome is caused by a weapon, thought to be a directed pulsed electromagnetic or acoustic device, used by our adversaries to disrupt American and Canadian diplomats and military personnel.  The other is that Havana Syndrome is nothing more than preexisting conditions or subjective symptoms caused by stress or perhaps environmental factors. All it would take is a cluster of diplomats with new onset migraines, for example, to create the belief in Havana Syndrome, which then takes on a life of its own.

Both hypotheses are at least plausible. Neither can be rejected based on basic science as impossible, and I would be cautious about rejecting either based on our preexisting biases or which narrative feels more satisfying. For a skeptic, the notion that this is all some kind of mass delusion is a very compelling explanation, and it may be true. If this turns out to be the case it would definitely be satisfying, and we can add Havana Syndrome to the list of historical mass delusions and those of us who lecture on skeptical topics can all add a slide to our Powerpoint presentations detailing this incident.

But I am not ready to do that. We need to go through due diligence. It remains possible that our adversaries have developed a device that can beam directed pulsed EM or acoustic energy over a moderate distance (say, 100 meters) and that they have been using such a device to experiment on its results, or to achieve some perceived goal of disrupting our diplomatic efforts. For those with a more conspiratorial mindset, this narrative is the most compelling.

While I view this story as a skeptic, I also view it as a neurologist. While all the symptoms being presented as Havana Syndrome are non-specific, meaning they can be caused by a lot of things, that does not mean they are not real. A lot of the symptoms are explainable as migraines, but that does not mean they are not triggered exogenously. In fact, that could make the claims a bit more plausible – the pulsed beam is triggering a migraine-like phenomenon in the brains of the targeted individuals. Not everyone would respond to such triggers, not all responses would be identical, and the symptoms induced can become chronic. Migraine-like phenomena would also not necessarily leave behind any objective pathological findings. We cannot see migraines on an MRI scan of the brain or in blood work or EEGs. Migraines are defined mostly by the subjective symptoms of those who suffer from them (with some subsets having mild findings on exam, such as autonomic symptoms).

The presence of neurological findings have been investigated. A 2019 study found some differences in the brains of people with reported AHIs. This was a small study, the findings were not necessarily what one would predict, and at most this was an exploratory study that generated some hypotheses to be further investigated. Now two recent studies have tried to replicate these results with larger sample sizes and some more detailed analysis – and they found no brain differences between those with AHIs and controls. While this is a blow to the Havana Syndrome hypothesis, it does not kill it entirely. As an accompanying editorial by Dr. Relman, who was involved in investigating subjects with AHI, points out, we would not necessarily see consistent brain imaging finding for a variety of reasons. He also criticizes the studies for not limiting their analysis to those with what he considers to be the cardinal feature of true Havana Syndrome – the location dependent aspect of the symptoms. This could have diluted out any real findings.

There are other ways to resolve the question about the true nature of Havana Syndrome. American intelligence agencies have investigated the question as a national security question, and they report finding no evidence of any program by a foreign power to develop or use such a device. Another approach is to study directed pulsed EM or acoustic device to see if we can replicate the symptoms of Havana Syndrome. This has not been done to date.

And here the controversy sits. So far it seems that the objective evidence favors the “mass delusion” hypothesis. This is similar to “sick building syndrome” and other health incidents where a chance cluster of symptoms leads to widespread reporting which is followed by confirmation bias and the background noise of stress and symptoms focusing on the alleged syndrome. This explanation, at least, cannot be ruled out by current evidence.

But I don’t think we can rule out that something physical is going on that so far has eluded detection. Relman focuses much of his arguments on the location-dependent symptoms reported by some individuals. That would be a strange and unique feature that favors and external phenomenon. But I don’t personally know how solid these reports are, if they were contaminated by suggestive history taking, or perhaps a coincidence magnified by faulty memory and pattern seeking behavior.

As we like to say – this questions needs more study. I don’t know how open a question there is from an intelligence perspective, or if they have closed the book on it. From a neurological perspective it seems like a follow up study, addressing the criticisms of the current studies, could lay the question to rest. But that will not resolve the underlying question, because there does not necessarily have to be an documentable brain changes for a migraine – like syndrome. Finally, there is the technology question. Is a directed pulsed EM or acoustic device workable, and will it reproduce the symptoms of Havana Syndrome. That might be the most definitive piece of evidence (short of the CIA catching a foreign agent red-handed with such a device).

I do think that if Havana Syndrome is real, we should be able to demonstrate it either through reproducing the technology or uncovering evidence of a foreign program to use it. The longer we go without definitive evidence, the more likely the mass delusion hypothesis becomes. The neurological approach is most useful in the positive – if we identify clear signs of Havana Syndrome in sufferers, that will go a long way to supporting its reality. But if these studies remain negative, that does not have the potential to falsify Havana Syndrome.