Havana Syndrome

Summary

American diplomats and intelligence officers began reporting a sudden sound, a sensation of pressure in the head, and then headaches, dizziness, cognitive difficulty and other persistent symptoms. It was widely reported as a directed-energy attack by a hostile state.

Two things are true at once, and both matter. The symptoms are real and in many cases severe, and the people reporting them are not lying. And the two largest investigations, one medical and one intelligence, have found no weapon, no adversary, and no detectable injury.

This record is written with care. It concerns living people who are unwell.

What is documented

The reports. From late 2016, United States government personnel in Havana reported an abrupt onset of symptoms, in many cases beginning with a perceived sound or a feeling of pressure in the head, and followed by headache, dizziness, tinnitus, cognitive difficulty, sleep disturbance and balance problems. Similar reports followed from other posts around the world. The US government uses the term Anomalous Health Incidents, and that shift in language is itself informative: an incident category, not a diagnosis.

The people are genuinely unwell. This is not in dispute anywhere in the literature, including in the studies that found no physical cause. Symptoms have been severe, prolonged, and career-ending for some of those affected. Any account of this case that treats the reporters as malingerers is not supported by any of the evidence.

The NIH studies (2024). Researchers at the NIH Clinical Center studied affected personnel and their family members over nearly five years, and published two papers in JAMA in March 2024.

They found no significant evidence of MRI-detectable brain injury. They found no consistent biological abnormality. On most clinical measures, the affected group did not differ significantly from matched controls.

They also found that the reported symptoms were real and, in many participants, severe. The finding is not that nothing happened to these people. The finding is that whatever happened did not leave the physical signature that a directed-energy weapon causing traumatic brain injury would be expected to leave.

The earlier finding they could not reproduce. An earlier study from the University of Pennsylvania had reported differences in the brains of affected personnel. The NIH team, with a larger cohort of 86 patients and better controls, was unable to replicate it.

The intelligence assessment. In 2023, five intelligence agencies concluded it was highly unlikely that the incidents resulted from a foreign attack, and that there was no credible evidence that a weapon capable of producing the reported effects even exists.

The Intelligence Community's updated unclassified assessment, current as of December 2024 and released in January 2025, holds that it is very unlikely or unlikely that a foreign actor was responsible. Five components emphasise that sensitive intelligence reporting continues to point away from foreign involvement, and that a review of foreign research into novel weapons found nothing.

The dissent, which is real and should be stated. Not every component agrees. Some hold different views about a small number of individual events, and one component has judged a roughly even chance of foreign involvement in a subset. Those dissenting judgments are held at low confidence, and the agencies holding them say so.

An earlier intelligence panel, in 2022, concluded that some episodes could plausibly have been caused by pulsed electromagnetic energy from an external source. That finding has not been withdrawn, and it is not the same as saying that this occurred.

A 2022 CIA review found that most of the symptoms attributed to the syndrome were attributable to pre-existing conditions or to stress.

Leading explanations

Mass sociogenic illness, or a comparable process. Not a claim that the symptoms are imagined. Mass psychogenic illness produces genuine, disabling physical symptoms with no organic lesion, and it is one of the best-documented phenomena in medicine. It requires a stressed population, a plausible threat, and a mechanism by which the belief propagates.

Diplomats and intelligence officers on hostile postings, in an environment of surveillance and physical risk, aware that colleagues had reported an attack, constitute exactly such a population. The absence of a detectable injury, the absence of a weapon, the absence of an adversary and the presence of severe real symptoms are all consistent with this, and it is the explanation the evidence most nearly fits.

Directed energy. The original hypothesis, and it has not been formally excluded. What it lacks is a weapon. No such device has been found, no adversary programme to build one has been identified, and the intelligence community has looked hard. The 2022 panel's judgment that pulsed electromagnetic energy could plausibly account for some cases stands as a possibility, not a finding.

Pre-existing conditions, environmental factors and stress. The CIA's 2022 review found this accounted for most reported cases. It does not obviously account for the abruptness of onset that many describe.

Crickets. In 2019, analysis of a recording made in Havana of the sound reported by personnel found it to be a close match for the call of the Indies short-tailed cricket. This is a real, published finding about a specific recording. It explains a sound. It does not, on its own, explain a syndrome.

Current status

Unsolved. The registry classifies this as unsolved rather than debunked, deliberately.

What has been substantially ruled out is the popular version: a hostile state with a directed-energy weapon, causing brain injury. That version does not survive contact with the medical evidence or the intelligence evidence.

What has not been established is what did happen. A large number of people became genuinely and in some cases permanently unwell, in a specific occupational population, in a specific decade, and the best explanation available is a psychogenic process that leaves no trace precisely because that is what such processes do. That explanation fits. It has not been demonstrated.

Last reviewed: July 2026. Records are provisional. Where the evidence changes, the entry changes. Found an error? Tell us.