Posttraumatic stress disorder is associated with reduced vitamin D levels and functional polymorphisms of the vitamin D binding-protein in a population-based sample.

•PTSD is associated with reduced vitamin D levels and vitamin D deficiency.•rs4588 and rs7041 of the vitamin D-binding protein are associated with vitamin D levels.•rs4588 and rs7041 are associated with PTSD, even after adjusting for vitamin D levels.•Homozygous carriers of the Gc2 genotype showed an increased risk for PTSD.