In a recent cohort study published in The Lancet Regional Health – Europe, researchers from Sweden and Finland conducted a population-based study to investigate the potential association between psychiatric disorders in parents and the risk of the offspring developing autism spectrum disorder (ASD).
They found that the highest risk of offspring ASD was observed in cases where both the parents had psychiatric disorders, with impacted mothers showing a higher risk compared to impacted fathers alone.
Study: Association between parental psychiatric disorders and risk of offspring autism spectrum disorder: a Swedish and Finnish population-based cohort study. Image Credit: Prostock-studio/Shutterstock.com
Background
Globally, more than 16% of adults have ASD. The condition is influenced by both heritable and non-heritable factors, with parental psychiatric disorders posing a significant risk. However, large population studies comparatively examining maternal and paternal psychiatric disorders and their combined influence on offspring ASD are lacking.
The complex genetic architecture of psychiatric disorders, with multiple alleles across various loci, may contribute to a higher risk. Current evidence on this association is fragmented and hindered by inconsistent results, methodological limitations, and potential confounding factors.
Therefore, leveraging data from Swedish and Finnish nationwide registers, researchers in the present study conducted a comprehensive analysis. They examined the potential link between parental psychiatric disorders and offspring ASD while considering parental gender, comorbidities, and specific psychiatric disorders.
About the study
The study included children born in Sweden (1997–2016) to Nordic parents (Sweden, Denmark, Finland, Iceland, or Norway). Data were sourced from the Swedish Medical Birth Register, the Swedish Multi-generation Register, and the Total Population Register. The study was replicated using data from children born to Nordic parents in Finland during the same period.
A total of 2,505,842 children (Sweden n = 1,488,920, Finland n = 1,016,922) were included and followed up for a mean of 11 years. Psychiatric disorder diagnoses were sourced from the Swedish National Patient Register and the Finnish Care Register for Health Care, utilizing the International Classification of Diseases (ICD) system.
In both Sweden and Finland, regular medical check-ups and developmental assessments are standard procedures for infants and preschoolers. Children showing signs of ASD are referred to specialists in child psychiatry or neurology for detailed evaluation, following established protocols for diagnosis.
Further, data on birth year, offspring sex, maternal/paternal age, gestational age, maternal body mass index, maternal smoking during pregnancy, parental income, and education were gathered for supplementary analyses.
Statistical analysis involved the use of Cox proportional hazards models, adjusted hazard ratios (aHRs), inverse Kaplan–Meier curves, and interaction term assessments, with robust standard errors and adjustment for offspring birth year.
Results and discussion
Of the total included children, 33,612 were found to be diagnosed with ASD. In Sweden, the prevalence was 1.65% in children without parental psychiatric diagnoses, rising to 2.67% when both parents were affected.
Pre-childbirth psychiatric diagnoses were found in 4.94% of fathers only, 8.24% of mothers only, and 1.63% of both parents. Affected parents were younger, less educated, had lower income, and their offspring were more likely to be preterm and diagnosed with autism earlier.
Psychiatric disorders, whether in fathers only (aHR = 1.59), mothers only (aHR = 1.95), or both parents (aHR = 2.34), were associated with an increased risk of ASD in the offspring, as compared to parents without diagnosed psychiatric disorders.
Additionally, the presence of comorbid psychiatric disorders in a parent further increased the risk of ASD in offspring. Similarly, in Finland, the risk of offspring ASD was found to be highest in cases of psychiatric disorders in both the parents (aHR = 3.61), followed by those in mothers only (aHR = 2.12) or fathers only (aHR = 1.63), as compared to parents without psychiatric disorders.
The offspring showed significantly higher ASD risk across all parental psychiatric disorder categories, with maternal diagnoses associated with higher risk, particularly in neurodevelopmental disorders, mood disorders, neurotic/behavioral disorders, and psychoactive substance use disorders. However, schizophrenia and non-mood psychotic disorders in either parent were found to increase the risk of offspring ASD equally.
The study is strengthened by its large-scale birth cohort with long-term follow-up, clinically ascertained psychiatric diagnoses, robust adjustment for confounding factors, and successful replication in the two countries.
However, the study shows limited statistical precision for specific parental psychiatric disorders, an inability to distinguish children raised by non-biological parents, a lack of adjustment for other parental confounding factors, and the absence of data on psychiatric disorders diagnosed in primary care visits, potentially biasing towards capturing severe cases.
Conclusion
In conclusion, the study found that 20% of children with ASD had at least one parent with psychiatric disorders.
The highest ASD risk was observed when both parents were affected, followed by cases with only the mother or father impacted.
Risk increased with the number of co-occurring disorders. All parental psychiatric conditions were associated with elevated ASD risk. The findings highlight the importance of assessing various parental psychiatric conditions to identify high-risk children for early interventions and improved outcomes.
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