When scientists study human behavior they make sure they link it to chemical substances and actions. Good thing, or we’d still be hanging witches and condemning people-who-don’t-belong to mental institutions for life.

This study, done on rhesus monkey moms and babies, demonstrates clearly that abusive moms often produce next-generation abusive moms (about half the time)–which fits the pattern of stats we find with human moms and babies. So when they searched for the chemical connection, the only difference they could identify was that the grew-up-to-be-abusive female monkeys had 10 to 20% lower levels of serotonin in their brains. Studies with rates showed the same pattern. “Low levels of serotonin are associated with anxiety and depression and impulsive aggression in both humans and monkeys.”

But the significant part of this is that this is the first study to show that it’s maternal behavior that changes brain chemistry first. The hope is that abused kids with lowered levels could be treated early with drugs to boost their serotonin and break the cycle of abuse. May we find a way soon.