An illness that mysteriously spread among US embassy staff in Cuba and was blamed on a suspected sonic attack was most likely caused by emotional trauma and fear, according to a new report.
At least 22 personnel were said to have been affected by unexplained hearing loss between the autumn of 2016 and the summer of last year, sparking a diplomatic row between the two countries.
The symptoms were blamed on a covert sonic device, which prompted American officials to order much of the staff stationed at the base in Havana to leave.
Scientists later suggested that the suspected sonic attacks, which also led to Canada pulling families of its own diplomats out of the Cuban capital, could have been caused by the sound of crickets.
But now a leading sociologist and an expert in neurodegenerative diseases have said it was most likely emotional trauma and fear that caused the symptoms - which included headaches, nausea and fatigue.
Dr Robert Bartholomew and study co-author Dr Robert W Baloh believe the so-called 'Havana Syndrome' is more akin to shell shock, a signature feature of which is concussion-like ailments.
They describe the diplomats who became sick as participants in a continuation of the Cold War, living in a hostile foreign country where they were under constant surveillance, causing stress and uncertainty.
Writing in the Journal of the Royal Society of Medicine, they said: "A characteristic feature of combat syndromes over the past century is the appearance of an array of neurological complaints from an overstimulated nervous system that are commonly misdiagnosed as concussions and brain damage.
"The political and scientific evidence for the perpetration of an attack on US embassy staff in Cuba is inconclusive."
Previous studies on the syndrome had "critical design flaws", the authors added - most importantly a lack of evidence that the personnel had been exposed to an energy source or toxin.
They said: "None adequately test the hypotheses they propose, while promoting exotic explanations that are not supported by the facts. Our conclusions are grounded in the prosaic and known science.
"There is no need to resort to exotic explanations. Claims that the patients were suffering from brain and auditory damage are not borne out by the data."