title: Autism spectrum disorder and low vitamin D at birth: a sibling control study.
abstract: BACKGROUND
  Insufficient vitamin D activity has attracted increasing interest as a possible underlying risk factor in disorders of the central nervous system, including autism.
  
  
  METHODS
  In this study, 25-hydroxyvitamin D (25(OH)D) was analysed in 58 Sweden-born sibling pairs, in which one child had autism spectrum disorder (ASD) and the other did not. The study group consisted of two representative samples; 47 Gothenburg sibling pairs with mixed ethnicities and 11 Stockholm sibling pairs with Somali background. 25(OH)D levels were analysed in the stored dried blood spots taken in the neonatal period for metabolic screening.
  
  
  RESULTS
  The collapsed group of children with ASD had significantly lower vitamin D levels (M = 24.0 nM, SD = 19.6) as compared with their siblings (M = 31.9 nM, SD = 27.7), according to a paired samples t-test (P = 0.013). The difference was - most likely - not only accounted for by a difference in season of birth between ASD and non-ASD siblings since the mean 25(OH)D levels differed with similar effect size between the sibling pairs born during winter and summer, respectively. All children with African/Middle East background, both the children with ASD and their non-ASD siblings, had vitamin D deficiency.
  
  
  CONCLUSIONS
  The findings suggest that low prenatal vitamin D may act as a risk factor for ASD, however, there is a need for replication with larger samples. Future research should study whether or not adequate supplementation of vitamin D to pregnant women might lower the risk for ASD in the offspring.
authors: Gillberg Neuropsychiatry Centre, Sahlgrenska Academy, University of Gothenburg, Kungsgatan 12, 411 19 Gothenburg, SE Sweden ; Research and Development Centre, Skaraborg's Hospital, Skövde, Sweden.
authors: Elisabeth
authors: E
authors: Fernell
authors: Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden ; Department of Psychiatry, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors: Susanne
authors: S
authors: Bejerot
authors: Department of Psychology, University of Stockholm, Stockholm, Sweden.
authors: Joakim
authors: J
authors: Westerlund
authors: Gillberg Neuropsychiatry Centre, Sahlgrenska Academy, University of Gothenburg, Kungsgatan 12, 411 19 Gothenburg, SE Sweden.
authors: Carmela
authors: C
authors: Miniscalco
authors: Queensland, Brain Institute, University of Queensland, Brisbane, Australia.
authors: Henry
authors: H
authors: Simila
authors: Queensland, Brain Institute, University of Queensland, Brisbane, Australia ; Queensland Centre for Mental Health Research, University of Queensland, Brisbane, Australia.
authors: Darryl
authors: D
authors: Eyles
authors: Gillberg Neuropsychiatry Centre, Sahlgrenska Academy, University of Gothenburg, Kungsgatan 12, 411 19 Gothenburg, SE Sweden.
authors: Christopher
authors: C
authors: Gillberg
authors: Department of Psychiatry, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors: Mats B
authors: MB
authors: Humble
keywords: 25-hydroxyvitamin D; Autism spectrum disorder; Dried blood spots; Neonatal; Vitamin D