Friedrich Nietzsche's famous quote, "What doesn't kill me makes me stronger," might never ring truer than in the case of male, Polish Jews who survived the Holocaust. A new study shows that men who survived the Holocaust as young boys, on average, lived longer than their peers who emigrated to the United States before the start of WWII.

The research, published by the U.S.-based Public Library of Science, compares the lives of 55,000 Polish Jews who emigrated to Israel before and after the war.What it discovers is that men who lived through the Holocaust as boys or young men lived as much as 18 months longer than those who didn't -- an astonishing finding that co-author Avi Sagi-Schwartz says could be attributed to a phenomenon known as "post-traumatic growth."

These findings are called into question by some, though, who consider the notion of differential mortality as a possible explanation for the longer life spans.

Sagi-Schwartz says the theory of differential mortality has proved contentious in Israel, where people are reluctant to believe that any of the Holocaust's estimated 6 million Jewish victims earned their fate because they were weakest. But he says it still merits consideration as a possible explanation for why male Holocaust survivors live longer.

"We know that the extermination was so brutal and systematic that even stronger people could not escape it," Sagi-Schwartz says. "But those who were not randomly selected to be exterminated immediately -- those who were living in ghettos, those who were in camps -- somehow managed to keep their life going on under very difficult circumstances, with lack of food, lack of medical services. So maybe the stronger managed to survive, and in that respect, we might see at least partly the explanation of differential mortality."

Daisy Sindelar over at The Atlantic does more to break down the findings and the differing opinions, including the suggestion that, if true, this theory should be mimicked by survivors of other major conflicts across the globe. [The Atlantic]