Objective: ADHD is a common neuropsychiatric disorder in children and adolescents. Experimental data of Vitamin D demonstrate that vitamin D has a remarkable role in proliferation, differentiation, neurotrophism, neuroprotection, neurotransmission, and neuroplasticity. Low levels of vitamin D were associated with depression, seasonal affective disorder, and schizophrenia in adults, but little is known about vitamin D effect on mental health in the pediatric population. In this study, we aimed to investigate serum vitamin D levels in pediatric ADHD patients.
Methods: The study population included 20 females and 32 males aged 6 to 17 years were admitted to the outpatient clinic of the Child and Adolescent Psychiatry Department, between March 2013 and February 2014. Serum 25-OH vitamin D levels of participants were collected on routine admission laboratory testing. Vitamin D levels were classified as low and normal; depends on seasonal norms basis Vitamin D levels (lower limit; 20 ng/ml for the summer, in winter 10 ng/ml). Patients, who met the criteria of the Diagnostic and Statistical Manual of Mental Disorders for ADHD, were recruited. Conners Parent Rating Scale (CPRS) and Conners Teacher Rating Scale (CTRS) scores, which were kept in the files of ADHD patients were calculated. Socio-demographic information as well as environmental risk factors that may play a role in the etiology, which may be related physical illness, comorbid diagnoses, ADHD subtypes were examined and the obtained data investigated the correlation between with vitamin D levels. Stroop Color-Word Test (ST) was used to evaluate the attentional functions. Average performance on the Stroop test was calculated based on total test time (ST-T), total error rate (ST-E), and correct response (ST-C) incorrectness.
Results: This study was conducted on 52 children with ADHD (32 (61.5%) boys, and 20 (38.5%) girls), aged between 6 and 17 years (mean±SD: 11.4±3.0 years). The mean serum 25-OH-vitamin D level was 17.4±9.8 ng/ml (for boys: 19.4±11.3, for girls: 14.4±5.5 ng/ml; p=0.08). Subjects with a history of frequent infections were more likely to have low levels of 25-(OH) vitamin-D in comparison to those without this history (p=0.011). The ST-C scores of ADHD patients having low serum vitamin D levels were significantly higher than those, who had normal Vitamin D levels (respectively, 2.9±2.7, 5.2±2.8 ng/ml, p=0.025).
Conclusion: Vitamin D deficiency could be associated with a number of psychiatric and neurological conditions. Multiple studies demonstrated that reduced DA and/or NE function hypothesis in ADHD. Abnormal dopamine regulation in certain areas of the central nervous system might have a role in the etiology of ADHD. In our study, results from Stroop Test and frequency of infection history in patients having low vitamin D levels refers to possible relationship between immune dysfunction and 25-(OH) vitamin-D deficiency. It should be investigated further prospective and controlled studies.