PERHAPS the most widespread peril children face isn’t guns, swimming pools or speeding cars. Rather, scientists are suggesting that it may be “toxic stress” early in life, or even before birth.

This month, the American Academy of Pediatrics is issuing a landmark warning that this toxic stress can harm children for life. I’m as skeptical as anyone of headlines from new medical studies (Coffee is good for you! Coffee is bad for you!), but that’s not what this is.

Rather, this is a “policy statement” from the premier association of pediatricians, based on two decades of scientific research. This has revolutionary implications for medicine and for how we can more effectively chip away at poverty and crime.

Toxic stress might arise from parental abuse of alcohol or drugs. It could occur in a home where children are threatened and beaten. It might derive from chronic neglect — a child cries without being cuddled. Affection seems to defuse toxic stress — keep those hugs and lullabies coming! — suggesting that the stress emerges when a child senses persistent threats but no protector.