He has studied the brains of rats, for whom parental care can be demonstrated in how much the mother grooms her pups.
"You can put two rats on a table and tell which one is raised by a low-licking mother. The one reared by a low-licking mother is more nervous, and fatter," Meaney said in an interview at the Psychiatric Association meeting.
Images of the brain cells of the rats show the brain cells of low-licking mothers have fewer dendrites. These are the strands that help one neuron communicate with another.
Meaney, who also worked on the suicide study, said the research, taken together, demonstrates how early experiences can cause physical changes in the brain.
He said female rats reared by low-licking mothers reached puberty earlier, meaning they had more offspring.
Similar findings are true of humans, who often have children at younger ages when times are stressful. The best way to pass along genes in uncertain times is to have more children, he said.
