Approximately 7.2% of children worldwide have attention-deficit hyperactivity disorder (ADHD) and some communities may have a prevalence as high as 15.5%, making it the most common neurodevelopment disorder in childhood. ADHD in childhood is associated with poor academic and social outcomes, and it may continue to affect quality of life into adulthood. Understanding the potential genetic, biological, and epigenetic factors that contribute to the development of ADHD and the impact of diet, lifestyle, and potential therapeutic factors may benefit those with ADHD. One recent area under investigation for its potential role in the development of and benefit to ADHD is vitamin D. 

Vitamin D may play a role in brain function, central nervous system (CNS) function, and mental health. It is considered a developmental neurosteroid. Vitamin D regulates calcium in the brain and participates in neuronal migration and growth, differentiation, neurotransmission, cell interaction, and synaptic function. Vitamin D also plays a key role in the development of the dopaminergic system, which also may be involved in ADHD. 

A meta-analysis of observational studies examined the difference in serum 25(OH)D levels in children and adolescents with ADHD compared to controls. In the eight trials included in this study, the patients with ADHD had significantly lower levels of serum 25(OH)D compared to the controls. The pooled data likewise demonstrated a significant difference between the group with ADHD and the control group. 

Some studies have also investigated the potential for vitamin D supplementation to act as an adjunct therapy for ADHD. One randomized controlled trial (RCT) in children aged 5 to 12 years with vitamin D insufficiency compared taking 2,000 IU vitamin D daily for 8 weeks as an adjunct treatment to the psychostimulant methylphenidate to a placebo. The group taking the vitamin D supplement experienced a significant increase in serum 25(OH)D levels. Both groups experienced an improvement in ADHD symptoms, but the vitamin D group experienced more improvement in evening symptoms, such as difficulty in completing homework, inattentiveness in tasks, excessive running, and trouble preparing for sleep. A meta-analysis of RCTs using vitamin D supplementation as an adjunct therapy to methylphenidate likewise found statistically significant improvement in ADHD symptoms.

A case-control prospective intervention study found that there was a significantly higher number of children with ADHD diagnosed with vitamin D deficiency compared with the control group and significantly lower values of serum 25(OH)D. In the group of ADHD children supplementing with vitamin D (3,000 IU daily for 8 weeks), there was an improvement in cognitive function, especially in the conceptual level, inattention, opposition, hyperactivity, and impulsivity domains. The children with ADHD who did not supplement with vitamin D experienced no improvement, except in the oppositional domain.

Research into vitamin D demonstrates that it has roles beyond supporting bone health. Vitamin D promotes normal brain function and development, making it a potential area to consider for conditions such as ADHD in children and adolescents. Dietary and lifestyle factors may aid in increasing vitamin D levels, but additional supplementation may support health including brain function.*  

By Kendra Whitmire, MS, CNS