In late 2016 U.S. diplomats and family members based in Cuba began reporting a wide swath of neurological symptoms, including dizziness, headaches, deafness and difficulty concentrating, following exposure to ear-splitting noises around their homes. This “Havana syndrome” outbreak disrupted U.S. relations with Cuba, spawned congressional hearings on the “attacks” and left some people with years of disabling symptoms. Reports from people with these symptoms also occurred in other countries, and the U.S. government labeled these cases as “anomalous health incidents” (AHIs).
The abrupt onset of these symptoms led to years of debate among scientists and those affected about possible causes, which ranged from pesticides to group psychology to noise from crickets. Now two medical studies that were conducted by the National Institutes of Health and released on Monday morning might finally have an answer. The researchers compared more than 80 of these affected individuals with similar healthy people. The results, detailed in the Journal of the American Medical Association, show no clinical signs or brain image indications to explain those widely varied symptoms. The JAMA findings follow the 2023 release of an intelligence community assessment that found that the injuries were not the result of foreign attacks. More likely, the assessment suggested, they were tied to previous injuries, stress, environmental concerns and “social factors” such as group psychology, in which illness symptoms reported by one individual in a community can spread serially among its members. Such outbreaks have been seen everywhere from hiccupping in high schools to “repetition strain” cases among Australian typists in the 1980s.
“These individuals have real symptoms and are going through a very tough time,” said NIH rehabilitation medicine expert Leighton Chan, who led one of the studies, at a briefing for reporters last Friday. Nothing in the new medical findings contradicts the assessment of the injuries in the intelligence community report, he said.
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In the first study, led by Chan, investigators examined 86 people with AHIs, 42 women and 44 men, who last experienced an incident 76 days prior, on average. The participants were U.S. government staff and family members who had been in locations that included parts of Cuba, China and Austria, as well as the U.S. (All of these areas were past sites of Havana syndrome outbreak reports.) A third of these affected participants were unable to work because of their symptoms. (According to Chan, a few of the cases dated to 2015, which was prior to the previously reported cases in Cuba.) Clinical tests for hearing, balance, cognition, eyesight and blood work were matched against the results from 30 people with similar working backgrounds but no symptoms. The researchers found that the only significant differences between the two groups were increased self-reported symptoms of fatigue, stress and depression in people with AHIs, as well as self-reported trouble with balancing that was confirmed through testing.
Likewise, in a second study that looked at brain imaging in 81 of the same participants compared with 48 controls, investigators led by Carlo Pierpaoli of the NIH’s National Institute of Biomedical Imaging and Bioengineering found “no significant differences in imaging measures of brain structure or function” among the two groups. The findings are consistent regardless of where the cases originated. Balance problems were the most pronounced complaint among the participants with AHIs: they were seen during tests in more than a quarter of those affected by this syndrome. These cases of persistent postural-perceptual dizziness point to a brain function disorder that the NIH researchers say could be linked to either external injuries or psychological distress.
Notably, these imaging findings contradict a 2018 JAMA study, which was widely reported in the news (with some scientific controversy) and found signs of concussion and possible brain injuries in a few people with Havana syndrome. The new NIH studies relied on advanced magnetic resonance imaging scanners used only in research, which likely showed a more accurate picture of any false positives, Pierpaoli said at the press briefing. In addition, whereas previous studies chose a narrow range of controls without the same background as those with Havana syndrome, in the new study, the researchers compared affected people with more representative individuals without symptoms.
The fact that the new studies found no discernible brain or clinical differences between affected and healthy participants, “should be some reassurance to the patients,” said neurologist Louis French of Walter Reed National Military Medical Center in Bethesda, Md., which is where many patients with AHIs have been treated and is near the NIH’s headquarters, during the press briefing. “This will allow us to focus on the here and now of getting back to where they should be.”
“People who were told by trusted authorities that they suffered brain damage from a secret weapon will likely dismiss the NIH report as a government cover-up,” says University of Maryland neuroscientist Douglas Fields. “It is, however, an excellent scientific study, with conclusions that are well supported by data, and the study will be viewed as highly credible by scientists.”
In a 2019 report investigators at the Centers for Disease Control and Prevention had suggested that a case-control study of people with Havana syndrome—the type of investigation used in the two new studies undertaken by the NIH researchers—might lead to “misleading or obscured findings” because of the time elapsed since the onset of symptoms. In the press event, Chan acknowledged this concern as a reason for caution in interpreting the new results but said a case-control study was the best option left to investigators.
He noted that the results do leave open the possibility of some external cause such as pulsed microwaves (suggested in a 2020 National Academies of Sciences, Engineering, and Medicine, or NASEM, report) having triggered injuries that then healed and left no signs before any of the clinical tests or brain scans were undertaken. Some of the affected participants were seen as soon as 14 days after an incident, Pierpaoli said, and showed no signs of differences with healthy controls.
“I suspect what we are seeing in leaving the door ajar to the possibility to more exotic explanations has less to do with the inability to understand psychologically induced symptoms and more with not wanting to embarrass colleagues,” says medical sociologist Robert Bartholomew, co-author of Havana Syndrome: Mass Psychogenic Illness and the Real Story Behind the Embassy Mystery and Hysteria. Bartholomew suggests the cases sprouted in classic mass psychology fashion, where high-status individuals (intelligence personnel) in a stressful environment (the U.S. embassy in Cuba) reported symptoms, leading to alarm spreading to their wider community (embassies worldwide). In this scenario, an outbreak of people suffering real psychological injuries resulted. “Clearly, the NIH study points to the role of conventional health issues in a population experiencing extraordinary stress,” Bartholomew says. “It’s time to put this episode behind us, heed the lessons and move on.”
Mark Zaid is an attorney who represents more than two dozen current and past federal officials, as well as family members, with Havana syndrome who are seeking continued medical treatment at Walter Reed. He questions the ethics of the NIH testing process, saying participation was seen as a requirement for treatment. (Chan strongly disputed this suggestion in the briefing.) Zaid voices concerns that the results would be used to wrongly dismiss Havana syndrome injuries. “The government is knowingly weaponizing the lack of science that exists in this area and intentionally hiding behind the classification wall where much of the evidence that contradicts the results exists,” he says.
In 2017, when word of Havana syndrome first broke, news reports widely suggested that “sonic weapons” had played a role. A year later news outlets replaced this claimed potential cause with “microwave” weapons. Then, by 2019, they suggested that “pulsed” microwaves explained the injuries, and the NASEM report later judged that idea as the most plausible cause late that year. Unknown to that report’s writers, a 2018 U.S. Department of State–sponsored technical report conducted by a highly regarded technical group called JASON, which was only declassified later, had already cast doubt on the theory that the injuries were caused by any kind of electromagnetic effect. (Crickets likely explained incident noises, it suggested.) Those doubts also appeared in a 2022 follow-on report from the same experts.
Still, in an editorial accompanying the new JAMA studies, Stanford University microbiologist David Relman, who chaired the NASEM report, maintains that pulsed microwaves might explain some injuries. Relman’s article cites wide variations in symptoms, the gap in timing between incidents and the NIH assessments and a wider lack of understanding of brain injury mechanisms from electromagnetic effects in general. In the editorial, he calls for “surveillance systems designed to rapidly detect early cases and clusters of concern.”
In the press event, Chan expressed concern that such surveillance might worsen symptoms in diplomats and intelligence personnel who are already under stress and trigger more persistent postural-perceptual dizziness cases where psychological distress plays a part in the malady. He noted that some affected people were from intelligence agencies, which makes communication about their circumstances trickier. (Regarding Chan’s concerns, “I think a surveillance system of the sort I described is a good idea,” Relman wrote in an e-mail to Scientific American.)
“It is reassuring that the people experiencing AHIs suffered no brain damage from their experience—but the evidence for that was never strong in any event,” said University of Pennsylvania health physicist Kenneth Foster to Scientific American. The possibility of attack by microwaves “still gives me pause,” he added. “The technology exists to give someone a frightening but not acutely damaging experience by inducing mechanical disturbances to the vestibular system using pulsed microwaves or laser light.”
Bartholomew is more skeptical. “They have essentially said, ‘We have not found any compelling evidence for Bigfoot’, but of course, Bigfoot could be there; we just didn’t see it,” he says.