UVB exposure from sunlight promotes the production of vitamin D and those who live in Scotland are twice as likely to be deficient in this vitamin compared to the rest of the UK due to low levels of sunlight during the winter months. Vitamin D is a crucial nutrient to the brain development of the foetus. Researchers also found that this link between low UVB exposure and learning disabilities is even stronger during early pregnancy within the first trimester. Therefore conceiving in winter raises the risk of learning disabilities. Looking at 422,500 school children the percentage of children with learning disabilities varied by month of conception, ranging from 16.5% among children conceived in July, to 21.0% among those conceived in February, March and April.

The study ‘Antenatal exposure to solar radiation and learning disabilities: Population cohort study of 422,512 children’ is published in Scientific Reports.

Pregnancy and sunlight

The challenge

The challenge was to investigate the seasonal patterning of learning disability and the hypothesis that this may be due to low vitamin D levels over the winter months. This is due to the importance in maternal vitamin D concentrations for normal brain development while being aware of variables such as sex (with more boys developing autism and other learning disabilities) and conception (with boys having a differing seasonal pattern of conception to girls).

The solution

The connection between UVB exposure and learning disabilities was explored by analysing total antenatal sunshine hours and UVB exposure. This was linked to the 2007-2016 Scottish School Pupil Censuses and Scottish maternity records to find out if there was a connection between low UVB exposure in pregnancy and learning disabilities. Logistic regression analyses were used to explore the associations between UVB and learning disabilities adjusting for the confounding effects of month of conception and sex. Significant connections were found with UVB exposure throughout pregnancy and particularly during the first trimester. This was found to be irrespective of UVA levels suggesting that the production of vitamin D produced by UVB exposure is the key link to the seasonal patterning of learning disabilities.

Impact and outcomes

Now that a link has been established between low UVB exposure in winter months and learning disability by month of conception further studies can be conducted to see if there are possible solutions that may help to prevent learning disabilities such as vitamin D supplements and to investigate whether vitamin D supplements can reduce seasonal patterning in learning disabilities.

Learning disabilities can have a massive effect on individuals, families and society. Identifying risk factors may reduce health and social care costs in society and help to prevent learning disabilities.

This study and the finding of a link between UVB exposure and learning disabilities emphasises the importance for pregnant women of taking vitamin D supplements.

Professor Jill Pell lead author of the study and Director of the University of Glasgow’s Institute of Health and Wellbeing said: “Learning disabilities can have profound life-long effects on both the affected child and their family. The importance of our study is it suggests a possible way to prevent learning disabilities in some children. Our findings reinforce the current recommendation that pregnant women should take vitamin D supplements … especially if they live in less sunny countries such as Scotland.”


Co authors: Professor Jill Pell and Dr Claire Hastie, University of Glasgow Institute of Health and Wellbeing

University of Edinburgh School of Geosciences

Scottish Government, ScotXed


Professor Jill Pell jill.pell@glasgow.ac.uk