A Spanish researcher believes he has uncovered the reason why some young men die suddenly after being arrested by police.

Manuel Martinez Selles of Madrid's Hospital Gregorio Maranon said young men who die after arrest may be the victims of a new syndrome similar to one that kills some wild animals when they are captured, Reuters reports.

Selles looked at 60 cases of sudden unexplained deaths in Spain following police detention. What he found was that in one-third of cases, death occurred at some point of the arrest, while the remainder of deaths occurred within 24 hours.

The average age of the victims was just 33-years-old and none had a history of heart troubles, according to the report.

"We know that when a wild animal is captured, sometimes the animal dies suddenly," Selles told the news agency."Probably when these young males are captured it is very stressful and their level of catecholamines goes very high and that can finish their life by ventricular fibrillation (cardiac arrest)."

Catecholamines are hormones produced by the adrenal glands. They are released into the blood during times of physical or emotional stress, according to the National Institutes of Health.

A doctor at Mount Sinai Medical Center in New York, who was not involved in the research, said the concept was "a reasonable hypothesis."

Selles presented his findings at the annual meeting of the European Society of Cardiology.

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