Consider this short post about the findings reported by Evangelia Kotsi and colleagues  an extension of some previous discussions on the topic of vitamin D levels and attention-deficit hyperactivity disorder (ADHD) (see here and see here).
The conclusion reached by Kotsi et al - "The systematic review and meta-analysis of observational studies demonstrated an inverse association between serum 25(OH)D and young patients with ADHD" - was not entirely unexpected given the results of other independent meta-analyses . They do however reiterate that in amongst the tons of research linking vitamin D deficiency / insufficiency to various labels (see here and see here for other examples), ADHD should perhaps be part of any future research strategy. Specifically, as the authors mention, the question is: "whether vitamin D-deficient infants are more likely to develop ADHD in the future?" (Perhaps.)
A couple of next research steps should also include: (a) a focus on the reason(s) for vitamin D deficiency / insufficiency in relation to ADHD (including the genetics angle) and (b) whether supplementation *might* be something that 'affects' the behavioural presentation of ADHD  as well as just physiological levels of the sunshine vitamin/hormone and hence should be considered an intervention? We'll see what happens.
 Kotsi E. et al. Vitamin D levels in children and adolescents with attention-deficit hyperactivity disorder (ADHD): a meta-analysis. Atten Defic Hyperact Disord. 2018 Oct 26.
 Khoshbakht Y. et al. Vitamin D Status and Attention Deficit Hyperactivity Disorder: A Systematic Review and Meta-Analysis of Observational Studies. Adv Nutr. 2018 Jan 1;9(1):9-20.
 Dehbokri N. et al. Effect of vitamin D treatment in children with attention-deficit hyperactivity disorder. World J Pediatr. 2018 Nov 19.