Henry VIII
Portrait of Henry VIII: Does he look angry to you? CC

It wasn't American football, but jousting that gave Henry VIII repeated head injuries so severe that it affected his behaviour, according to an intriguing new theory by researchers from Yale University. The king was "lighthearted, merry and easily given to laughter" in his early days but turned explosive, despotic and cruel later on, just like modern-day sufferers of repeated head trauma.

"It is intriguing to think that modern European history may have changed forever because of a blow to the head," said Arash Salardini, instructor in behavioral neurology at Yale School of Medicine and senior author of a new study on Henry VIII. Salardini pored over letters and other documents and biographies to determine that Henry actually suffered several head injuries from 1524 and 1536, while he was still in his thirties.

In 1524, a lance penetrated the visor of his helmet and knocked him off his horse, which left him dazed. In 1525 he was knocked unconscious when he fell as he tried to vault over a stream. His most serious injury was in 1536, when he fell off his horse while jousting and the horse then fell on top of him. Henry went "for two hours without speaking," according to reports at the time, which Salardini and his assistants interpreted to mean he was unconscious.

After the first injury, Henry began to suffer from migraines, which grew in severity. There were also reports of insomnia, signs of depression and the king's increasingly murderous rage.

He also had memory problems, "characteristic of subcortical amnesia sometimes seen in traumatic brain injury," the scientists write in a study to be published in June in the Journal of Clinical Neuroscience. He was so befuddled at one point that he forgot his role in his son's funeral just two days after the fact.

He also had another symptom of brain injury: impotence, according to both Anne Boleyn and Catherine Howard, say the researchers. "Historians agree his behavior changed after 1536,'' said Salardini, noting that descriptions of Henry during his youth portrayed an intelligent and even-tempered young man who made wise military and policy decisions.

His behavior in the later years of his life became notoriously erratic: He was forgetful and prone to rages and impulsive decisions. Traumatic brain injury, Salardini believes, best explains most of Henry's abnormalities.