How Does Vitamin D Relate to Tic Disorders and Associated Conditions in Children?

What you need to know

• Contrary to previous smaller studies, this large study found that children with chronic tic disorders did not have lower vitamin D levels than unaffected children.
• Lower vitamin D levels were associated with higher rates of ADHD and more severe ADHD symptoms in children with tic disorders.
• Vitamin D levels were not related to tic severity or OCD symptoms in children with tic disorders.
• More research is needed to determine if vitamin D plays a causal role in ADHD symptoms in children with tic disorders.

Background on tic disorders and vitamin D

Chronic tic disorders, including Tourette syndrome, are neurodevelopmental conditions that cause involuntary movements or vocalizations called tics. These disorders often begin in childhood and can significantly impact quality of life. Many children with tic disorders also have other conditions like attention-deficit/hyperactivity disorder (ADHD) or obsessive-compulsive disorder (OCD).

Vitamin D is an important nutrient that our bodies produce when our skin is exposed to sunlight. It plays many roles in the body, including helping with bone health and immune function. Some studies have suggested vitamin D may also be important for brain development and function.

A few small studies had previously found that children with tic disorders tended to have lower vitamin D levels. This led to interest in whether vitamin D deficiency could be involved in causing or worsening tics. However, larger studies were needed to confirm this potential link.

About this study

This study was part of a large European project called EMTICS that examined children with tic disorders. The researchers measured vitamin D levels in:

• 327 children with chronic tic disorders
• 31 children who developed tics during the study period
• 93 children without tics who were siblings of children with tic disorders

They compared vitamin D levels between these groups and looked at whether vitamin D was related to tic severity or symptoms of ADHD and OCD.

Key findings on vitamin D and tics

Contrary to expectations based on previous smaller studies, this study found:

• Children with chronic tic disorders did not have lower vitamin D levels than unaffected children. In fact, vitamin D levels were slightly higher in the tic disorder group.
• Vitamin D levels were not associated with tic severity in children who had tic disorders.
• There was no significant difference in vitamin D levels between children who developed tics during the study and those who did not.

These results suggest that low vitamin D is likely not a major factor in causing or worsening tics in most children.

Findings on vitamin D and associated conditions

While vitamin D was not linked to tics themselves, the study did find some interesting associations with other conditions that often occur alongside tic disorders:

• Children with tic disorders who had lower vitamin D levels were more likely to also have ADHD.
• Lower vitamin D was associated with more severe ADHD symptoms in children with tic disorders. This was true for overall ADHD symptoms as well as inattention symptoms specifically.
• Surprisingly, higher vitamin D levels were associated with slightly higher rates of OCD in children with tic disorders. However, vitamin D levels were not related to OCD symptom severity.

What do these results mean?

This study provides strong evidence that low vitamin D is likely not a major cause of tics in most children, despite what some smaller studies had suggested. Parents of children with tic disorders do not need to be overly concerned about vitamin D in relation to tics specifically.

However, the link between lower vitamin D and higher rates of ADHD symptoms in children with tic disorders is intriguing. This aligns with some previous research finding associations between vitamin D and ADHD in children without tics as well.

It’s important to note that this type of study cannot prove that low vitamin D directly causes or worsens ADHD symptoms. There could be other explanations for the association. For example, children with more severe ADHD may spend less time outdoors and therefore have lower vitamin D levels.

The unexpected finding of higher vitamin D being linked to slightly higher OCD rates is difficult to interpret. Since vitamin D wasn’t related to OCD symptom severity, this may have been a chance finding. More research would be needed to determine if there’s truly a meaningful relationship there.

Limitations of the study

While this was a large, well-designed study, it did have some limitations:

• Vitamin D levels were only measured once for each child. Levels can fluctuate over time.
• The study didn’t have a separate healthy control group - it compared children with tics to unaffected siblings.
• Information wasn’t available on factors that could influence vitamin D levels, like time spent outdoors, diet, and supplement use.

Conclusions

• Low vitamin D does not appear to be a major factor in tic disorders for most children, contrary to what some earlier small studies suggested.
• The association between lower vitamin D and higher ADHD symptoms in children with tics is intriguing and warrants further research.
• Children with tic disorders who have ADHD symptoms may potentially benefit from vitamin D testing and supplementation if levels are low, though more studies are needed.
• All children should maintain adequate vitamin D levels for general health, regardless of whether they have tics.

This study highlights the importance of large, well-designed studies to confirm or refute findings from smaller preliminary studies. It also demonstrates how examining related conditions like ADHD can reveal important associations even when the primary outcome (tics in this case) shows no relationship.

Future research could examine whether vitamin D supplementation improves ADHD symptoms in children with tic disorders who have low vitamin D levels. Studies that track vitamin D levels and symptoms over time could also help clarify whether low vitamin D plays a causal role or is simply associated with ADHD symptoms for other reasons.

For now, parents of children with tic disorders should focus on overall health, including maintaining adequate vitamin D, rather than viewing vitamin D as a specific treatment for tics. Children with both tics and ADHD symptoms may particularly benefit from having their vitamin D levels checked and optimized.