Summary: Children of mothers who experience more negative moods as a result of postpartum depression during the first two months of their child’s life have less mature processing of speech sounds at the age of six months.
Source: Max Planck Institute
Up to 70 percent of mothers develop postnatal depressive mood, also known as baby blues, after their baby is born. Analyses show that this can also affect the development of the children themselves and their speech. Until now, however, it was unclear exactly how this impairment manifests itself in early language development in infants.
In a study, scientists at the Max Planck Institute for Human Cognitive and Brain Sciences in Leipzig have now investigated how well babies can distinguish speech sounds from one another depending on their mother’s mood.
This ability is considered an important prerequisite for the further steps towards a well-developed language. If sounds can be distinguished from one another, individual words can also be distinguished from one another.
It became clear that if mothers indicate a more negative mood two months after birth, their children show on average a less mature processing of speech sounds at the age of six months. The infants found it particularly difficult to distinguish between syllable-pitches.
Specifically, they showed that the development of their so-called Mismatch Response was delayed than in those whose mothers were in a more positive mood. This Mismatch Response in turn serves as a measure of how well someone can separate sounds from one another.
If this development towards a pronounced mismatch reaction is delayed, this is considered an indication of an increased risk of suffering from a speech disorder later in life.
“We suspect that the affected mothers use less infant-directed-speech,” explains Gesa Schaadt, postdoc at MPI CBS, professor of development in childhood and adolescence at FU Berlin and first author of the study, which has now appeared in the journal JAMA Network Open.
“They probably use less pitch variation when directing speech to their infants.” This also leads to a more limited perception of different pitches in the children, she said. This perception, in turn, is considered a prerequisite for further language development.
The results show how important it is that parents use infant-directed speech for the further language development of their children. Infant-directed speech that varies greatly in pitch, emphasizes certain parts of words more clearly – and thus focuses the little ones’ attention on what is being said – is considered appropriate for children. Mothers, in turn, who suffer from depressive mood, often use more monotonous, less infant-directed speech.
“To ensure the proper development of young children, appropriate support is also needed for mothers who suffer from mild upsets that often do not yet require treatment,” Schaadt says. That doesn’t necessarily have to be organized intervention measures. “Sometimes it just takes the fathers to be more involved.”
Notes: The researchers investigated these relationships with the help of 46 mothers who reported different moods after giving birth. Their moods were measured using a standardized questionnaire typically used to diagnose postnatal upset. They also used electroencephalography (EEG), which helps to measure how well babies can distinguish speech sounds from one another.
The so-called Mismatch Response is used for this purpose, in which a specific EEG signal shows how well the brain processes and distinguishes between different speech sounds.
The researchers recorded this reaction in the babies at the ages of two and six months while they were presented with various syllables such as “ba,” “ga” and “bu”.
Association of Postpartum Maternal Mood With Infant Speech Perception at 2 and 6.5 Months of Age
Language development builds on speech perception, with early disruptions increasing the risk for later language difficulties. Although a major postpartum depressive episode is associated with language development, this association has not been investigated among infants of mothers experiencing a depressed mood at subclinical levels after birth, even though such a mood is frequently present in the first weeks after birth. Understanding whether subclinical depressed maternal mood after birth is associated with early language development is important given opportunities of coping strategies for subclinical depressed mood.
To examine whether depressed maternal mood at subclinical levels 2 months after birth is associated with infant speech perception trajectories from ages 2 to 6.5 months.
Design, Setting, and Participants
In this longitudinal cohort study conducted between January 1, 2018, and October 31, 2019, 46 healthy, monolingual German mother-infant dyads were tested. The sample was recruited from the infants database of the Max Planck Institute for Human Cognitive and Brain Sciences. Initial statistical analysis was performed between January 1 and March 31, 2021; the moderation analysis (results reported herein) was conducted between July 1 and July 31, 2022.
Mothers reported postpartum mood via the German version of the Edinburgh Postnatal Depression Scale (higher scores indicated higher levels of depressed mood, with a cutoff of 13 points indicating a high probability of clinical depression) when their infants were 2 months old.
Main Outcomes and Measures
Electrophysiological correlates of infant speech perception (mismatch response to speech stimuli) were tested when the infants were aged 2 months (initial assessment) and 6.5 months (follow-up).
A total of 46 mothers (mean [SD] age, 32.1 [3.8] years) and their 2-month-old children (mean [SD] age, 9.6 [1.2] weeks; 23 girls and 23 boys) participated at the initial assessment, and 36 mothers (mean [SD] age, 32.2 [4.1] years) and their then 6.5-month-old children (mean [SD] age, 28.4 [1.5 weeks; 18 girls and 18 boys) participated at follow-up. Moderation analyses revealed that more depressed maternal subclinical postpartum mood (mean [SD] Edinburgh Postnatal Depression Scale score, 4.8 [3.6]) was associated with weaker longitudinal changes of infants’ electrophysiological brain responses to syllable pitch speech information from ages 2 to 6.5 months (coefficient: 0.68; 95% CI, 0.03-1.33; P = .04).
Conclusions and Relevance
The results of this cohort study suggest that infant speech perception trajectories are correlated with subclinical depressed mood in postpartum mothers. This finding lays the groundwork for future research on early support for caregivers experiencing depressed mood to have a positive association with children’s language development.