Havana Syndrome, also known as anomalous health incidents (AHIs), represents a cluster of acute and chronic neurological symptoms such as headache, imbalance, vertigo, and cognitive problems. [1]

Two prestigious expert panels, one from the National Academies of Sciences, Engineering, and Medicine and another from the Intelligence Community, concluded that pulsed radiofrequency energy could plausibly account for some distinctive AHI symptoms. [2, 3]

However, the expert panels were unable to pinpoint an exact mechanism of injury. Moreover, although some medical studies reported objective differences in AHI patients, others did not. [4, 5]

The lack of clarity about the cause of AHI symptoms and the inconsistent results led some experts to assert that AHI represents a case of mass hysteria, formally known as mass psychogenic illness (MPI). [6]

What is Mass Psychogenic Illness (MPI)?

MPI is the rapid spread of physical symptoms through a cohesive social group in the absence of an identifiable organic cause, propagated by visual, verbal, or media transmission of belief and anxiety. [7]

MPI spreads through social networks rather than according to proximity to a source, with a predominance among females and younger people. Typically, the index case is someone with high status or visibility. [7]

Common symptoms include headache, dizziness, nausea, hyperventilation, fainting, chest tightness, weakness, paresthesias, and abdominal pain. Motor forms add tremor, tics, psychogenic seizures, gait disturbance, and dysphonia. [7]

Four examples cited in the literature are:

Tanganyika laughter epidemic, 1962 — uncontrollable laughing and crying spread through mission schools for months, forcing closures. [8]
West Bank schoolgirls, 1983 — nearly 1,000 Palestinians, mostly girls, reported fainting, headache, and abdominal pain; competing allegations of poison gas circulated, but investigators found no toxic cause. [9]
Le Roy, NY, 2011–12 — Tourette-like tics emerged among high-school girls; environmental hypotheses were investigated, and social media may have contributed to the spread. [10]
Contemporary “TikTok tics” (2020–21) — functional tic-like behaviors were reported in young people during a period of extensive social-media exposure, showing that the “group” need not be physically co-located. [11]

MPI researchers describe underlying psychological mechanisms that include: [7]

The nocebo effect (experiencing an adverse result one expects)
Heightened attention to interoceptive cues, amplifying ordinary sensations until they seem pathological
Acute stress and autonomic arousal, with subsequent reactions interpreted as signs of illness
Automatic, unconscious mimicry and “social contagion”
A compelling narrative: “Y caused X.”

The case for MPI causing Anomalous Health Experiences

Medical sociologist Dr. Robert Bartholomew and neurologist Dr. Robert Baloh argue in their book, Havana Syndrome: Mass Psychogenic Illness and the Real Story Behind the Embassy Mystery and Hysteria, that AHI is a classic example of MPI. [6]

Indeed, there is overlap between the symptoms of AHI and those reported in some cases of MPI, such as headache, dizziness, and nausea. There is also overlap with some proposed predisposing conditions for MPI, such as social contagion through the news, acute stress, and a narrative that directed-energy weapons wielded by foreign adversaries caused AHI.

Bartholomew and Baloh discount the possibility that pulsed RF or toxins could be responsible, arguing, for instance, that there is no evidence such an RF weapon is possible. Bartholomew went so far as to call proposed RF attacks “science fiction” and to say that “humans have a remarkable capacity for self-deception.” [6, 12]

Dr. Baloh went further: “The idea that a sonic weapon caused selective brain or inner ear damage is not physically possible…” [13]

The case against Mass Psychogenic Illness

As the former Associate Director of National Intelligence overseeing science and technology for the entire Intelligence Community, and author of The Spy in Moscow Station (which describes Russian microwave attacks on U.S. embassies), I am far less confident than Bartholomew and Baloh that an RF weapon capable of causing AHI is physically impossible.

In fact, I recently published a piece on this site describing how, through proposed mechanisms of brain damage such as cavitation and mechanical deformation of brain parenchyma, a pulsed RF weapon could inflict injury. [14]

Together with my wife, Chris Gilbert, MD, PhD, I have developed and tested a high-fidelity simulation of the head, brain, and inner ear that encompasses pulsed RF field concentration in tissue, heat generation in that tissue, pressure buildup from that heat, thermoacoustic pressure transients, and tissue strain and deformation produced by thermoacoustic pressure waves inside the skull. Our results suggest –but do not prove–multiple plausible mechanisms by which pulsed RF could inflict injury, consistent with reports from AHI patients. Our results echo and extend those of Army Research Laboratory scientists exploring the effects of pulsed RF on the brain. [15]

But let’s put that aside for the moment—along with press reports that a U.S. government agency acquired a suspected AHI-related RF device and that the Pentagon tested it—and consider the MPI hypothesis on its merits. [16] There are multiple aspects of the AHI story that do not align with the MPI theory:

An NSA employee reported an incident predating the highly publicized Havana cases. Social contagion from reports about Havana cannot explain an earlier report. [17]
The sudden onset of acute pain, pressure, ear fullness, and directional sounds reported in AHI cases differs from the symptoms typically described in MPI outbreaks. [1, 2, 7]
Multiple AHI patients report that symptoms started when they entered a particular area, stopped when they left, and started again when they reentered. [1, 18]
Several medical studies reported objective clinical findings, including vestibular and oculomotor abnormalities, although later studies did not find corresponding group differences on all measures. [18, 19]
Autopsy studies of people who experienced brain trauma have identified microscopic damage despite unremarkable gross examination, showing that physical injury can be difficult to detect with routine assessment. [20]
Several individuals reported symptom onset while alone, at night, in their own residences, before they knew of a wider group of cases. This raises a question about how social transmission would account for the earliest reports. [2, 18]
Classic MPI outbreaks can be explosive and self-limiting, with remission after separation and reassurance. A subset of Havana patients have reported symptoms persisting for years despite dispersal and treatment. [2, 7, 19]
MPI often spreads through social networks; early Havana cases involved personnel who reported limited awareness of one another’s symptoms. [2, 7]
Some affected individuals report having been dismissive of colleagues’ claims before their own onset—the reverse of the expectation a nocebo explanation would require. [2]

What does it all mean?

The MPI hypothesis represents a valid possibility that cannot be entirely discounted simply because it does not explain multiple AHI phenomena.

Given that more than a thousand government employees have reported AHI symptoms, it is possible that at least some of them may have been experiencing MPI. [21]

But the balance of the evidence—even discounting objective medical findings and the conclusions of expert panels that considered the pulsed RF hypothesis—weighs against MPI as the sole cause of AHI.

Certainly, even though the mechanism of AHI injury remains uncertain, there is enough doubt about the MPI theory that statements calling physical causes of AHI “science fiction” or “impossible” seem to go further than the data warrant.

That is why my wife, Chris, and I, who are deeply involved in AHI research and have interviewed half a dozen people reporting AHI, are careful about the language we use to describe our results. We acknowledge substantial gaps in scientific knowledge about how pulsed RF affects the brain and vestibular system.

We use terms such as “possible,” “plausible,” and occasionally “likely” or “unlikely,” but we avoid absolutes such as “science fiction” or “physically impossible.”

One reason is that, if there is a physical cause of AHI, confident assertions that “it’s all in the victims’ heads” risk doubly victimizing people who have already suffered.

We do not want to add to the suffering of people who report AHI, some of whom have seen their careers end or suffer because they spoke up, in addition to experiencing physical and emotional distress.

It is one thing to suffer; it is quite another to have the reality of your suffering discounted with absolute certainty.

Thus, Chris and I try to live by the old saying: “Keep your words soft and sweet. You never know which ones you’ll eat.”