Postpartum Depressive Mood Linked to Infant Speech Development

Postpartum depressed mood in mothers appears to be correlated with infant speech perception trajectories, a population-based cohort study showed.

In a sample of 46 mothers, depressed subclinical postpartum mood (mean Edinburgh Postnatal Depression Scale [EPDS] score 4.8) was associated with weaker longitudinal changes in infants’ electrophysical brain responses to syllable pitch speech information from the ages of 2 to 6.5 months (coefficient 0.68, 95% CI 0.03-1.33, P=0.04), reported Gesa Schaadt, PhD, of Freie Universität Berlin in Germany, and colleagues.

While moderation analyses of the consonant, vowel, and vowel length mismatch response did not significantly explain overall variance, the authors did find significantly explained overall variance only for the syllable pitch mismatch response (R²=0.12, 95% CI 0.00-0.32, P=0.04), with a nonsignificant intercept (coefficient -2.41, 95% CI -5.90 to 0.12, P=0.08), suggesting a mismatch response change from positive to more negative amplitudes between the ages of 2 and 6.5 months.

“This finding means that mismatch response development (typically from positive to more negative values) stagnates or even becomes more positive (immature) at age 6.5 months with more depressed maternal mood and that this association becomes significant at EPDS scores of 8.57 or higher,” the authors wrote in JAMA Network Open.

The foundations of language development are already being established during the first few weeks after birth and build on speech perception, they explained, with early disruptions increasing the risk of later language difficulties.

“Our findings extend previous reports on negative associations between maternal postpartum clinically depressed mood and children’s language development by exploring the subclinical range of maternal mood,” Schaadt and team wrote. “They align with previous work suggesting that a reduction of infant-directed speech use among mothers with depressed mood is associated with children’s developmental trajectories.”

“Infant-directed speech uses greater pitch variability and slower speech rate compared with adult-directed speech and is critical for encouraging early language perception. However, depressed mothers often show a reduction in vocal pitch modulation when directing speech toward their infants,” they continued.

For this longitudinal cohort study, the authors recruited 46 healthy German mother-infant dyads from the Max Planck Institute for Human Cognitive and Brain Sciences database from January 2018 through October 2019.

Mothers had a mean age of 32, did not smoke, and did not have a history of neurotoxin use. All mothers were on maternity leave through the duration of the study period and were part of a joint household with two parents.

They reported postpartum mood via the German version of the EPDS when their infants were 2 months old. Scores range from 1 to 30, with higher scores indicating higher levels of depressed mood, and a cutoff of 13 points indicating a high probability of clinical depression.

Electrophysiological correlates of infant speech perception (mismatch response to speech stimuli) were tested when the infants were 2 months and 6.5 months.

There was an even split between infant boys and girls at both the initial assessment at 2 months and follow-up at 6.5 months.

Exclusion criteria for infants included gestational age less than 37 weeks, birth weight less than 2,700 g, and diagnoses of hearing deficits or neurologic conditions.

Schaadt and team acknowledged that correlation over time did not imply causation. In addition, mothers’ vocal pitch range was not tested, which was a limitation. Finally, maternal mood was only assessed when infants were 2 months old.

They suggested that further studies need to be conducted with more heterogenous samples for more generalizable results.