A massive population study reveals that postpartum depression in either parent, especially in both, may signal a substantially higher likelihood of autism in their child, underscoring the importance of early mental-health support for families.
Study: The association between parental postpartum depression and offspring autism spectrum disorder. Image credit: Bogdan Sonjachnyj/Shutterstock.com
Parental postpartum depression is associated with increased risk of autism spectrum disorder in infants, as reported by a new study published in Frontiers in Psychiatry.
Understanding post-partum risk
Postpartum depression is a type of moderate-to-severe depression that happens to parents after having a newborn. It affects up to 20% of new mothers. Recent evidence suggests that having a history of depression significantly increases the risk of developing postpartum depression.
Psychiatric history of parents has been linked to an increased risk of neurodevelopmental disorders in newborns. Autism spectrum disorder (ASD) is one such highly heritable neurodevelopmental disorder, with symptoms often appearing well before its clinical diagnosis around the age of two to three years.
Recent evidence suggests that maternal psychiatric disorders before pregnancy have a more pronounced influence on an infant’s ASD risk than paternal psychiatric disorders. However, the risk is highest in infants with both parents having a psychiatric history. Despite substantial evidence linking parental psychiatric history with neurodevelopmental conditions in infants, studies investigating the impact of parental postpartum depression on infants’ ASD risk are largely unavailable.
Researchers from the Icahn School of Medicine at Mount Sinai, USA, and Karolinska Institutet, Sweden, recently addressed this gap in the literature to gain insight into the intergenerational transmission risk for neurodevelopmental outcomes, including ASD.
The study population comprised all live births in Sweden between 1997 and 2021, who were followed up until December 31, 2022.
Identified ASD risk patterns
The study analysis included a total of 1,781,349 infants. In the entire study population, the highest prevalence of ASD was observed among infants with both parents diagnosed with postpartum depression (8.8 %), followed by infants born to fathers with postpartum depression (5.3 %) and infants born to mothers with postpartum depression (4.6 %).
These estimates corresponded to 2.59-times, 2.56-times, and 5.5-times higher relative risks of ASD among infants with mothers, fathers, and both parents diagnosed with postpartum depression, respectively.
The analysis adjusting for parental depression history, parental age, education, income, and preterm delivery showed a 1.7-times, 1.5-times, and 2-times higher risk of ASD among infants with mothers, fathers, and both parents diagnosed with postpartum depression, respectively.
The analysis, further adjusting for parental antidepressant use, any psychiatric history, and pre-delivery antidepressant use, did not lead to additional reductions in the magnitude of the observed associations.
Genetics and environment
The study identifies a significant association between parental postpartum depression and increased risk of ASD in infants. According to the findings, the risk of ASD in infants increases at a similar rate if either of the parents is diagnosed with postpartum depression. However, infants with both parents diagnosed with postpartum depression are at the highest risk of developing ASD.
Notably, the study finds a partial reduction in the magnitude of observed associations when potential confounding factors, including parental history of depression, antidepressant use, or any psychiatric history before delivery, are adjusted in the analysis.
The time surrounding birth is a critical time for early developmental events in infants. Several studies have linked parental depression to adverse neurodevelopmental consequences in infants, including cognitive and speech impairments, behavioral issues, poor adjustment, growth delay, and lack of fine motor skills.
However, it largely remains unknown whether these adversities are associated explicitly with parental postpartum depression, parental depression, or other psychiatric disorders. Although genetic factors play a substantial role in triggering neurodevelopmental complications in infants, a possible contribution of environmental risk factors and their interactions with genetic risk factors must be considered.
Existing evidence highlights that genes inherited from parents play a major role in ASD pathogenesis. The current study's observations of increased ASD risk due to maternal and paternal postpartum depression, and the highest ASD risk due to parental (both mother and father) postpartum depression, suggest that common genetic variants may be inherited from both parents.
Notably, the study finds that this combined risk from parental postpartum depression is reduced when the analysis is adjusted for the depression history of parents, highlighting the shared impact of genetic and environmental factors on ASD risk.
The Swedish National Patient Register (NPR) was used in the study to obtain diagnoses of depression. Since this register does not include diagnoses from primary care, the study could not analyze data from individuals with depression who did not visit health care facilities.
Furthermore, the study could not include parents with ASD diagnosed exclusively before 1987 because of data unavailability. Parental ASD might be a potential confounding factor that needs to be addressed in future studies. Genetic confounding may also have occurred if parents with postpartum depression are a specific group with a higher inherited risk of ASD.
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