Season of Conception/Birth and Learning Disability

The CLAHRC WM Director was long aware that the season of conception/birth is correlated with the risk of developing schizophrenia.[1] That autism is also correlated with reproductive chronicity comes as a surprise to him.[2] It seems, however, to be a robust finding, since it is supported by a Scottish linkage study across educational and maternity records.[3] There was a highly statistically significant increased risk of autism and dyslexia among children conceived in the first quarter of the year, and this was not present for other neurological disorders, such as motor disorders (‘cerebral palsy’). The effect size was modest (about 11% relative risk increase) in this study of over 800,000 children. The cause of the association is unclear, but some viral infections and low vitamin D levels in mid-Winter are obvious (and potentially remediable) candidates. In the first News Blog of 2017 we shall discuss further a methodological limitation of database studies and how this problem may be mitigated. In the meantime, let’s add the above paper to our ever-growing list of imaginative and important linkage studies.

— Richard Lilford, CLAHRC WM Director


  1. Castrogiovanni P, Iapichino S, Pacchierotti C, et al. Season of birth in psychiatry. A review. Neuropsychology. 1998; 37(4): 175-81.
  2. Mazumdar S, Liu KY, Susser E, et al. The Disappearing Seasonality of Autism Conceptions in California. PLoS One. 2012; 7(7): e41265.
  3. Mackay DF, Smith GCS, Cooper S-A, et al. Month of Conception and Learning Disabilities: A Record-Linkage Study of 801,592 Children. Am J Epidemiol. 2016; 184(7): 485-93.

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