ADHD is one of the most common neurodevlopmental psychiatric disorders. Many factors have been identified as the cause of ADHD. ADHD is thought to be the result of interactions between biopsychosocial factors leading to neurobiliogcal change. The aim of this study is to investigate the association between serum level of vitamin D and symptoms of attention deficit hyperactivity disorder (ADHD).

This is a case-control study which was conducted in children below 12years of age from June 2013 to May 2014 at outpatient child psychiatry clinic at Elhussin Hospital Al-Azhar University, Cairo, Egypt.

The study was based on 62 cases and 30 controls. The data collection instrument included socio-demographic & Children Attention and Adjustment Survey (House form){CAAS}. And interview by (Diagnostic Interview Kiddie-Sads-Present and Lifetime Version (K-SADS-PL) to exclude other psychiatric morbidity. clinical data, serum 25(OH) Vitamin D. Descriptive statistical analysis were performed, Pearson Chi² test (χ²) and Student (t) test.

1-Vitamin D level was much lower in ADHD children compared to healthy children, and was a significant difference in the mean values of vitamin D between ADHD(23±13) and control group means (44±12) and P value was>0.001 and was significant difference between subgroup of ADHD, means of inattentive subtype was(20±13) hyper active subtype (30.1±5)and combined subtype(24.04±4). P value 0.011^*.

Children with ADHD had significantly lower levels of VITAMIN D than healthy, and inattention subtype than other types of ADHD.