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And those gene changes could still be causing neurological problems that make young people more prone to depression and suicide, say the scientists at St. Michael’s Hospital and the University of Toronto.

The hypothesis might partially explain an unusual fact: suicide rates in indigenous communities were minimal before the mid-1980s and now are among the highest in the world.

“Suicide is not a traditional aspect of indigenous culture in Canada,” the article notes. “This commentary raises the possibility that the effects of tetraethyl lead poisoning during the 1970s and 1980s contributed to the rise in suicides, and continues to contribute to the growing problem through epigenetic modifcations.”

No one suggests the inter-generational legacy of toxic lead — if proven true by more study — would turn out to be the sole cause of the spate of suicides.

But it would add an intriguing risk factor to those more commonly cited, including feelings of hopelessness in impoverished communities, personal and family histories of mental illness or addiction, childhood abuse and the knock-on impact of the residential-school era.

“I think it is a contributing factor, but I don’t think it’s the primary one,” said Trehani Fonseka, the article’s co-author and a leader of the First Nations depression and suicide-prevention program at St. Michael’s. “It’s not just going to be one thing, there are going to be a lot of interactions between environmental risk factors and the biological ones, too.”