The new study shows that childhood experiences that fall well short of abuse, or even of having a mother who is depressed, leave their marks on our DNA. Led by Marilyn Essex, professor in the Department of Psychiatry and director of the Life Stress & Human Development Lab of the University of Wisconsin, Madison, scientists gave questionnaires to hundreds of parents, who were part of a years-long study, when their kids were infants and again when they were 3½ and 4½ years old.