Autism spectrum disorder (ASD) is a developmental disorder characterized by pervasive deficits in social interaction, impairment in verbal and non-verbal communication, and stereotyped patterns of interests and activities. Vitamin D deficiency has been previously reported in autistic children. However, the
data on the relationship between Vitamin D deficiency and the severity of autism are limited. 

In this study the researchers performed a case-controlled cross-sectional analysis on 122 ASD children, to assess their Vitamin D status compared to controls and the relationship between the degree of Vitamin D deficiency and the severity of autism.

They then conducted an open trial of Vitamin D supplementation in ASD children.
Fifty-seven percent of the patients in the study had Vitamin D deficiency, and 30% had Vitamin D insufficiency. The Vitamin D levels in patients with severe autism were significantly lower than those in patients with mild/moderate autism. Vitamin D levels had significant negative correlations with Childhood Autism Rating Scale (CARS) scores. 

kg/day (not to exceed 5000 IU/day) for 3 months. Eighty-three subjects completed 3 months of daily vitamin D treatment. 

80.72% (67/83) of subjects who received Vitamin D3 treatment had significantly improved outcome, which was mainly in the sections of the Childhood Autism Rating Scale and aberrant behavior checklist subscales that measure behavior, stereotypye, eye contact, and attention span. Of the 16 parameters measured, 10 showed highly statistically significant improvements (see table below)

Parameter	P Value (* highly statistically significant)
Relating to people	<0.001*
Emotional Response	<0.001*
Imitation	<0.001*
Body use	0.01*
Object use	0.01*
Adaption to change	0.004*
Listening response	0.01*
Taste, smell, touch	0.1
Visual response	0.003*
Fear	0.13
Verbal communication	0.3
Activity level	0.32
Non-verbal communication	0.2
Intellectual response	0.1
General impression	<0.001*
Total CARS score	<.001*

The authors concluded that as Vitamin D is inexpensive, readily available and safe. It may have beneficial effects in ASD subjects, especially when the final serum level is more than 40 ng/ml. 

Vitamin D status in autism spectrum disorders and the efficacy of vitamin Dsupplementation in autistic children.