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Researching the impact of postnatal depression on early language development

Christa Lam-Cassettari, Research Fellow from MARCS Institute’s Baby lab, Western Sydney University

How much impact does Postnatal Depression (PND) have on the conversation between a mother and her baby? And how does this conversation affect the child’s future development? These are the questions that have driven Christa Lam-Cassettari, Research Fellow from MARCS Institute’s Baby lab, Western Sydney University, to research what is known to be a critical time in infant development and speech formation.

“Talking to babies before they learn to speak is key to their brain development,” Christa explains.

“I wanted to look at how having PND might impact the conversations between mums and their babies.”

With a successful grant from South West Sydney Research’ Small Grant Scheme, Christa conducted research into the effect of PND on the expression of positive affect and pitch, the quality of mother’s infant-directed speech input and the timing of vocal responses between the mother and her baby. The results of the study were published this month in PLOS ONE.

The study used audio-recordings the of interaction between 26 mothers (13 mothers with PND and 13 without PND), and their six-month old babies. The study found that mothers with PND used less infant-directed speech and less exaggerated pitch than mothers without PND, who it was found, also spoke more to their babies and with more positive expression.

The importance of infant-directed speech (IDS) has been shown in multiple studies: that is, infants who experience less IDS show poorer language development.

“As an infant researcher, it is important to understand how children and babies learn so we can optimise their learning. This study gives us a baseline of understanding how PND can impact this learning,” she explains.

Christa acknowledges that although the study provided useful information, further study was needed to determine whether this difference in interaction results in differences in language development.

“The study is really a snapshot of what was happening when the babies were five-to-six months old. In terms of research this is really important but we needed follow-up data and a larger study.”

Understanding the limitations of the first study, Christa has followed up with a study in which babies aged between eight and 15 months wore a recorder for a whole day (the previous study was a recording of a five-minute play session).

Participants of the second study include 15 mothers who were clinically diagnosed with depression, 15 control mums with no PND and 13 mums who had a past history of depression but who were not depressed at the time of the study.

“Using a day-long recorder means we have been able to get greater insight about what is going on. We followed up these children once they were beginning to say their first words and gave them a vocabulary checklist to gauge how many  words the toddlers could understand and how many words they could say so we could obtain a measure of their early language skills.”

“The aim of this study is to identify similarities and differences in the number of words and conversational turns used by mothers and their infants across day long interactions and how this contributes to early vocabulary development in groups of infants where mothers have a clinical diagnosis of PND and mothers who do not,” Christa explains.

Christa is determined that her research has a positive impact on young children and their caregivers.

“My goal is to build knowledge and evidence to impact the day-to-day lives of children and their carers.

“Children are born with so much potential and I want to know how we can harness this potential so that they can develop into happy, healthy adults.”

Christa’s passion for infant research impressed South West Sydney Research, who not only awarded her a SWSR Small Grant in 2016/2017, but also sponsored her as a mentee in this year’s Franklin Women’s program.

“The Franklin Women’s Mentoring Program has made me examine my career trajectory and made me more determined to continue a path in research to make a difference in people’s lives.”


For more information on Christa’s work go to: