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Objective: The effects of vitamin D on human brain has begun to attract more attention; more extensive research has been carried out to understand the role of this vitamin on the development of human brain and childhood psychiatric disorders. The aim of this study is to examine whether Vitamin D deficiency is related to mental development, autism and behavioral problems. We also aimed to examine the relationship between global developmental delay and autism and Neural Growth Factor (NGF), Glial Cell Line-Derived Neurotrophic Factor (GDNF) levels, which are candidate biomarkers for explaining the possible relationship. Patients aged two-five years, who were admitted with developmental delay, constitute the sample of the study. There were two phases in the study. In the first phase, cases were classified due to vitamin D levels as low level of vitamin D and normal level of vitamin D groups. NGF and GDNF levels of cases were measured. Ankara development scanning inventory (AGTE) and Denver II development test were applied to the cases. Parents were asked to fill out autism behavioral checklist (ABC), and child behavior checklist (CBCL) 1.5-5 form. Psychiatric assessments regarding cases were carried out based on DSM-5. Later, global development delay (GDD) and global development delay- autism spectrum disorder (GDD- ASD) were created as two diagnostic subcategories. Both cases with normal vitamin D level and cases diagnosed with vitamin D deficiency were directed to special education program. The latter group also received vitamin D replacement treatment. After six months, control assessments of cases were carried out for the second phase of the study. Changes of checklist scores and in NGF and GDNF levels between groups receiving and not receiving vitamin D treatment were analyzed in control assessment.
Results: No significant difference in checklist scores and NGF and GDNF levels between patients with a normal vitamin D level and the ones with deficiency of vitamin D was observed. No difference in NGF and GDNF levels was observed among patients diagnosed with GDD and GDD-ASD. Significant negative relationship was found between vitamin D level and NGF levels. In addition, it was observed that only patients diagnosed with global development delay had a significant positive relationship between AGTE scores and GDNF levels. In control assessment, decrease in scores of ABC and progress in Denver II development scores were determined in the group receiving vitamin D replacement. Besides, more significant increase of NGF levels in GDD-ASD group and of GDNF levels in GDD was determined.
Conclusion: Findings of this study make us think that NGF could mainly intervene the effects of vitamin D in patients with ASD diagnosis while GDNF has more probability of intervening this effect in patients with GDD diagnosis and again It can be concluded from these findings that GDNF might be considered as an indicator of cognitive development, whereas NGF might be a more related to autistic disorders.