Vitamin D, Pregnancy, and Brain Development: Implications for ADHD and Autism

Some of the most compelling evidence linking vitamin D to mental health comes not from adult supplementation studies but from research on early life vitamin D status and later neurodevelopmental outcomes. This research has significant implications for pregnancy, early childhood, and our understanding of conditions like ADHD and autism.

The 2025 Danish Study: A Major Contribution

A landmark 2025 case-cohort study from Denmark analyzed nearly 90,000 individuals, measuring vitamin D from neonatal dried blood spots (blood collected shortly after birth). The findings were striking:

Schizophrenia: An inverse relationship between neonatal vitamin D and schizophrenia risk (HR: 0.82). The researchers estimated that optimizing neonatal vitamin D status could potentially prevent 15% of schizophrenia cases.

ADHD: Lower neonatal vitamin D was associated with increased ADHD risk (HR: 0.89). Potentially 9% of cases could be prevented by optimizing vitamin D.

Autism Spectrum Disorder: A similar pattern (HR: 0.93), with an estimated 5% of cases potentially preventable.

These are substantial population-level implications if the associations are causal.

Important Caveats

Before this information causes alarm or prompts drastic action, several important points deserve emphasis:

Association is not causation. While the study used Mendelian randomization to support causal inference, this is not definitive proof. Other unmeasured factors could contribute to both low vitamin D and increased neurodevelopmental risk.

Genetics and environment matter enormously. Even if vitamin D plays a role, these conditions have complex multifactorial origins. Vitamin D status is one factor among many.

We cannot change the past. If you or your child already have one of these conditions, this research does not mean vitamin D deficiency caused it. And supplementation now will not undo developmental effects.

Prevention is different from treatment. The developmental window hypothesis suggests vitamin D matters most during critical periods of brain development. Adult supplementation does not necessarily address developmental effects.

Why Development Matters for Vitamin D

The brain develops rapidly during pregnancy and early childhood, with critical periods when specific systems are forming. Vitamin D affects several developmental processes:

Neuronal differentiation: Vitamin D influences how neurons develop and specialize.

Axonal connectivity: The formation of connections between brain regions may be affected by vitamin D status.

Dopamine system development: Animal models show that vitamin D deficiency during development alters how the dopamine system forms and functions in adulthood. This is particularly relevant given dopamine’s role in ADHD and schizophrenia.

Once these developmental windows close, the opportunity to influence these processes passes. This is why neonatal vitamin D status may matter more than adult status for these specific conditions.

The Surprising Anorexia Finding

Intriguingly, the Danish study found an opposite pattern for anorexia nervosa: higher neonatal vitamin D was associated with increased risk (HR: 1.15). The researchers suggest that neurodevelopmental disorders and anorexia might be “reciprocal outcomes” associated with vitamin D status, though this remains speculative.

This finding is a reminder that biological relationships are often more complex than simple “more is better” narratives suggest.

Practical Implications for Pregnancy and Early Childhood

Current prenatal vitamin recommendations typically include 400 to 600 IU of vitamin D, which may be insufficient for many women to achieve adequate blood levels. Some experts recommend higher doses during pregnancy, though this remains an area of active research and debate.

If you are pregnant or planning pregnancy, discuss vitamin D testing and supplementation with your healthcare provider. Achieving adequate (not excessive) vitamin D status is a reasonable goal supported by this research, though optimal targets remain uncertain.

For parents of children with ADHD or autism, this research should not induce guilt or prompt aggressive supplementation. These conditions have complex causes, and vitamin D status is at most one contributing factor among many. Focus on evidence-based treatments for the conditions themselves.

For Adults: Your Vitamin D Status Still Matters

Even if early life vitamin D has unique developmental importance, adult vitamin D status is still relevant for current mental health. The research on adult depression and vitamin D operates through different mechanisms than developmental effects. You can not change your neonatal vitamin D status, but you can optimize your current levels.

References

1. Horsdal HT, Albiñana C, Zhu Z, et al. Convergent evidence linking neonatal vitamin D status and risk of neurodevelopmental disorders: A Danish case-cohort study. The Lancet Psychiatry. 2025;12(6):410-420.
2. Albiñana C, Boelt SG, Cohen AS, et al. Developmental exposure to vitamin D deficiency and subsequent risk of schizophrenia. Schizophrenia Research. 2022;247:26-32.
3. Eyles DW, Burne TH, McGrath JJ. Vitamin D, effects on brain development, adult brain function and the links between low levels of vitamin D and neuropsychiatric disease. Frontiers in Neuroendocrinology. 2013;34(1):47-64.
4. Rihal V, Khan H, Kaur A, Singh TG, Abdel-Daim MM. Therapeutic and mechanistic intervention of vitamin D in neuropsychiatric disorders. Psychiatry Research. 2022;317:114782.