PsM Vilja Seppälä defended her PhD thesis on the 21st October 2026. In her doctoral dissertation in psychology, Vilja Seppälä examined the associations of early childhood vitamin D supplementation and blood vitamin D levels with child neurodevelopment. The opponent was Associate Professor Rebecca Vinding from the University of Copenhagen. The custos was Professor Kati Heinonen-Tuomaala, the leader of the Developmental Origins of Mind Lab.
The thesis findings indicate that, among healthy term-born children, the currently recommended daily vitamin D supplement dose of 10 µg (400 IU) is sufficient from the perspective of neurodevelopment. However, maternal blood vitamin D levels during pregnancy, as well as child blood vitamin D levels during early childhood, were associated with child neurodevelopment. These findings suggest that, although vitamin D is likely involved in child neurodevelopment, as indicated by previous research, the relationship is complex and cannot be explained by vitamin D intake alone. Increasing the supplementation dose to 30 µg (1200 IU) does not appear to improve neurodevelopmental outcomes. The dissertation examines the topic at the population level and highlights that, based on previous literature, there is considerable individual variation in vitamin D absorption and metabolism.
The thesis consist of three publications:
Child sleep: https://doi.org/10.1016/j.sleep.2026.108913
Child neurocognition: https://doi.org/10.1007/s00787-025-02891-7
Maternal depressive symptoms: https://doi.org/10.1155/2024/1788167