Scientific Abstract

Background: Despite a large translational literature documenting the role of low maternal nurturance and elevated glucocorticoid production on offspring limbic development, these pathways have not yet been assessed during human infancy. Based on existing animal models, the present study examined whether 1) maternal disrupted interaction was related to infant cortisol levels, 2) infant cortisol levels were associated with limbic volumes, and 3) infant cortisol levels mediated the link between maternal disrupted interaction and infant limbic volumes.

Methods: Participants included 57 mother-infant dyads. Infant saliva was measured at three points before and after the Still Face Procedure (SFP) at 4 months infant age. Maternal disrupted interactions were coded during the SFP reunion. Between 4 and 24 months (M age = 12.28 months, SD = 5.99), under natural sleep, infants completed an MRI. Amygdala and hippocampal volumes were extracted via automated segmentation.

Results: Results indicated that 1) maternal disorientation in interaction with the infant was significantly associated with higher infant salivary cortisol (AUCg) levels, 2) infant AUCg was related to enlarged bilateral amygdala and hippocampal volumes, and 3) infant AUCg mediated the relation between maternal disorientation and infant amygdala and hippocampal volumes.

Conclusions: Findings are consistent with controlled translational studies and provide the first evidence of a link between increased cortisol levels and enlarged limbic volumes among human infants. Results also suggest that established interventions to decrease maternal disrupted interaction could impact both infant cortisol levels and infant limbic volumes.