WASHINGTON — U.S. intelligence agencies have determined that a foreign adversary is “very unlikely” to be responsible for the mysterious ailments known as Havana syndrome that American spies and diplomats have reported experiencing at missions around the world since 2016, officials announced on Wednesday.
The assessment builds on interim findings from the Central Intelligence Agency last year that neither Russia nor another hostile power was responsible for a global campaign targeting intelligence officers and diplomats who reported a wide range of symptoms such as headaches, dizziness and balance problems. In many of these cases, the patients said the symptoms began after they heard a strange sound and felt intense pressure in their heads.
But the conclusions released on Wednesday were broader, finding that none of the episodes the government investigated could be attributed to hostile foreign action.
The intelligence community assessment found that while seven different agencies had varying levels of confidence, most “concluded it is ‘very unlikely’ a foreign adversary is responsible” for the reported ailments. As part of the investigation, U.S. spy agencies reviewed intelligence, which showed that adversaries were puzzled and thought the reported symptoms were part of an American plot.
Some researchers, including in a 2020 report from the National Academy of Sciences, have said a microwave device or weapon using pulsed directed energy was the most probable cause.
But on Wednesday, the spy agencies concluded that there was no “credible evidence” that any adversaries had developed a weapon or an intelligence-collection device capable of causing the injuries that American officials have reported. However, a team of experts at the Pentagon is continuing to investigate the matter.
The mystery ailments have been referred to as Havana syndrome because the first known cases were reported by C.I.A. officers in the Cuban capital in 2016. Cases were subsequently reported by intelligence officers, diplomats and other U.S. government employees in China, Austria and dozens of other countries.
The Havana Syndrome Mystery
What is the Havana Syndrome? The mysterious illness, which has affected military officers, C.I.A. personnel and diplomats around the world, manifests itself in a host of ailments such as chronic headache, vertigo and nausea.
William J. Burns, the C.I.A. director, said in a statement that the findings reflected more than two years of “rigorous, painstaking collection, investigative work, and analysis” by the C.I.A. and other U.S. intelligence agencies.
“I and my leadership team stand firmly behind the work conducted and the findings,” Mr. Burns said. “I want to be absolutely clear: These findings do not call into question the experiences and real health issues that U.S. government personnel and their family members — including C.I.A.’s own officers — have reported while serving our country.”
Many patients who worked for the C.I.A. and the State Department complained that their ailments were not taken seriously for much of the Trump administration.
That began to change in 2020 — toward the end of the Trump administration — when officials expanded efforts to collect information about suspected Havana syndrome cases, and the C.I.A., the State Department and other agencies asked their employees to report any such incidents.
That led to an explosion in the number of possible cases, from dozens to some 1500.
In 2021, under the Biden administration, the C.I.A. and other intelligence agencies put more resources into investigating what may have caused the syndrome, initially raising the hopes of patients that the perpetrator or perpetrators would be identified. But as officials investigated the hundreds of reports that came in, it became clear that there was not a single set of symptoms, but rather a whole array of ailments that clinically looked very different.
Wednesday’s announcement was upsetting news for many patients, because they believe it cast doubt on the legitimacy of their injuries. Years later some of the affected people are still dealing with serious health problems that have prevented them from returning to work.
Mark Zaid, a lawyer who represents several patients with Havana syndrome, said that the assessment would undermine morale and that the intelligence agencies needed to provide more details about their work.
“The latest U.S. intelligence assessment lacks transparency, and we continue to question the accuracy of the alleged findings,” Mr. Zaid said.
Intelligence officials insisted their investigation over the past two years has been deep and rigorous, spending months hunting down individual leads — all to come up empty in finding any sort of global explanation that explained multiple incidents.
Intelligence agencies examined phones, laptops and other devices that were reported to show anomalies at the same time as patients first reported experiencing some symptoms.
The intelligence community, often referred to as the I.C., also sought to collect information about what potential adversaries were saying about these incidents to determine what they might know about them.
“Despite intensive and comprehensive efforts, the I.C. has not identified any compelling leads that have withstood scrutiny and point to foreign actors,” a statement by the National Intelligence Council said.
Intelligence officials also said researchers’ understanding of Havana syndrome and its medical effects have evolved since the initial reports in 2016 and 2017. At the time, some researchers believed they were seeing a “novel medical syndrome or consistent pattern of injury similar to traumatic brain injury,” the intelligence assessment said.
Those findings led some panels of experts to conclude the neurological injuries seen in the mysterious events were unlikely to be “explained by natural or environmental factors.” But intelligence officials said that newer research has undermined those initial conclusions, and suggests that a variety of environmental factors could cause some of the ailments that had been reported.
The report said that the spy agencies “assess that symptoms reported by U.S. personnel were probably the result of factors that did not involve a foreign adversary, such as pre-existing conditions, conventional illnesses, and environmental factors.”
Some patients have said that by dismissing theories that a foreign actor is responsible, the Biden administration is suggesting that it believes the Havana syndrome cases were the result of psychosomatic reactions or so-called functional illnesses.
U.S. intelligence officials on Wednesday would not address whether they thought the reactions were psychosomatic. An expert panel convened by the Biden administration last year found that neither stress nor psychosomatic reactions could explain the injuries that occurred.
Since the first Havana syndrome cases were reported in 2016, members of Congress have been pushing for better treatment and compensation for diplomats and C.I.A. officers who reported the ailments. They introduced and passed legislation to help compensate government employees who were injured.
As a result of the Havana Act, the U.S. government has begun paying compensation to C.I.A. officers, State Department diplomats and other officials who have been diagnosed with head injuries following reported incidents. Officials said on Wednesday those payments would continue despite the intelligence agencies’ findings.
Mr. Zaid said it was critical that the federal government continue its support for people who have been injured in the mysterious incidents.
“We implore all federal agencies with victims to ensure top-of-the line and long-term health care treatment is freely and timely made available to them and their families, as well as award proper compensation for injuries that for some have ended their careers in the line of service,” Mr. Zaid said.