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, found no weapon, no adversary, and no detectable injury. In June 2026 the Director of National Intelligence rescinded the intelligence assessments, and the Department of Defense has tested a device that some investigators suspect is linked to the incidents.

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 more than 80 participants and better controls, was unable to replicate it.

The intelligence assessment. In March 2023, five intelligence agencies judged it very unlikely that a foreign adversary was responsible, and the assessment found no credible evidence that a foreign adversary has a weapon or collection device that is causing the incidents.

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 base that judgment on sensitive intelligence reporting that continues to point away from foreign involvement, on investigations of key incidents, and on a review of foreign intelligence and research on novel weapons. Both the 2023 and the 2025 assessments were rescinded by the Director of National Intelligence in June 2026.

The dissent, which is real and should be stated. Not every component agrees. Two components changed their views in this update. One judges it likely that a foreign actor has a radio-frequency antipersonnel capability that can cause biological effects, while still judging it unlikely that such a weapon was used in any reported incident. The other judges a roughly even chance that a foreign actor used a novel weapon or prototype device to harm a small, undetermined subset of personnel. 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, an interim assessment issued in January 2022, found that most reported cases could be explained by environmental factors, undiagnosed medical conditions or 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 argued for by, among others, the neurologist Robert Baloh and the sociologist Robert Bartholomew (2020).

Directed energy. The original hypothesis, and it has not been formally excluded. What it lacks is a demonstrated link to any incident. In late 2024 Homeland Security Investigations bought a portable device that emits pulsed radio-frequency energy and contains Russian components, and the Department of Defense has tested it; no finding has been published. In the January 2025 assessment, one intelligence component judged it likely, at low confidence, that a foreign actor has a radio-frequency antipersonnel capability that can cause biological effects. 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 finding, posted as a preprint, 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.

The popular version, a hostile state causing brain injury with a directed-energy weapon, is not supported by the published medical evidence, and no intelligence or medical agency has published a finding that establishes it. The intelligence assessments that judged foreign involvement very unlikely were rescinded in June 2026.

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 no explanation has been demonstrated. A psychogenic process is consistent with the absence of detectable injury. A directed-energy cause has been neither demonstrated nor excluded.

Developments in 2026. In January 2026, CNN and CBS News reported that the Department of Defense had spent more than a year testing a portable device, bought by Homeland Security Investigations in late 2024, that emits pulsed radio-frequency energy and contains Russian components. No finding from that testing has been published. In June 2026 the Director of National Intelligence, Tulsi Gabbard, rescinded the 2023 and January 2025 assessments, stating that they had selectively excluded relevant intelligence, suppressed alternative analysis and relied on an ethically flawed medical study. The rescission did not attribute the incidents to any foreign actor, and no replacement assessment has been published. By July 2026 the Department of Defense had renamed its Anomalous Health Incidents team the Directed Energy Bio-Effects team.

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