A developmental decline in the learning-promoting effects of infant-directed speech for infants of mothers with chronically elevated symptoms of depression.

Infants of mothers who varied in symptoms of depression were tested at 4 and 12 months of age for their ability to associate a segment of an unfamiliar non-depressed mother's infant-directed speech (IDS) with a face. At 4 months, all infants learned the voice-face association. At 12 months, despite the fact that none of the mothers were still clinically depressed, infants of mothers with chronically elevated self-reported depressive symptoms, and infants of mothers with elevated self-reported depressive symptoms at 4 months but not 12 months, on average did not learn the association. For infants of mothers diagnosed with depression in remission, learning at 12 months was negatively correlated with the postpartum duration of the mother's depressive episode. At neither age did extent of pitch modulation in the IDS segments correlate with infant learning. However, learning scores at 12 months correlated significantly with concurrent maternal reports of infant receptive language development. The roles of the duration and timing of maternal depressive symptoms are discussed.