AND BABY MAKES 4 - PREDICTORS OF ATTACHMENT SECURITY AMONG PRESCHOOL-AGE FIRSTBORNS DURING THE TRANSITION TO SIBLINGHOOD

The present study examined preschool-age firstborns' adjustment to sib linghood, as indexed by security of firstborn-mother attachment, in a sample of 194 2-parent families. Security of firstborn attachment decr eased significantly after a secondborn's birth, but the size of the de crease was smaller among firstborns under 24 months relative to 2-5-ye ar-olds. Mothers' marital harmony and affective involvement with first borns predicted firstborn security before and after the baby's birth, whereas mothers' psychiatric symptoms predicted firstborn security onl y after the birth. Post-hoc analyses of select subgroups revealed that mothers of firstborns with high security scores before the newborn's birth, regardless of whether scores remained high or dropped after the birth, showed higher levels of psychosocial and behavioral functionin g than did mothers of firstborns with consistently low security scores at both time points. However, substantial drops in firstborn security after a secondborn's birth were associated with higher maternal psych iatric symptom scores both prior to and following the birth. Results s uggest that quality of firstborn adjustment to siblinghood can be pred icted from both structural and familial aspects of the firstborn envir onment.