Last updated on July 2019

Vitamin D as a Therapeutic Adjunct in the Stimulant Treatment of ADHD

Brief description of study

Specific Aim 1: As part of a within-subject, two-days, study design, to determine whether acute calcitriol (vs. placebo) pre-treatment is associated with greater amphetamine (Amp)-induced dopamine (DA) release in the caudate, putamen, ventral striatum (VST), and substantia nigra / ventral tegmental area (SN/VTA) of healthy human subjects.

Specific Aim 2: To determine whether acute calcitriol (vs. placebo) pre-treatment is associated with better performance on a test of attention (e.g., the continuous Performance Task or CPT-AX), after treatment with amphetamine. Hypothesis: Investigators hypothesize that Subjects pre-treated with calcitriol will have faster reaction times/higher accuracy on the CPT-AX vs. subjects pre-treated with placebo, after treatment with amphetamine.

Detailed Study Description

Increases in the rates of childhood ADHD over the past two decades have lead to speculation that calcitriol deficiency (e.g., secondary to the increased use of sunscreen and/or increases in sedentary, indoor lifestyles in children) plays a causal/contributory role in the etiology of ADHD. To date, evidence of a direct link is lacking. One study showed higher maternal circulating Vitamin D levels in pregnancy are associated with lower risk of developing ADHD-like symptoms in childhood. On the other hand, another study did not replicate the above association, and a prospective study using umbilical cord samples stored at the time of birth reported no difference in serum vitamin D levels between ADHD group versus healthy controls. In terms of clinical trials, one randomized double blind study among adults with ADHD reported a beneficial effect of the intervention, measured with the Conners Adult ADHR rating scale, in comparison with placebo, but the intervention included the combination of vitamin D and several other micronutrients. An analysis of moderators of a positive response to ADHD behaviors did not reveal a significant predictive effect of vitamin D.

However, recent studies provide intriguing indirect evidence of an inverse relationship between solar intensity (SI) and/or altitude (a proxy for greater sun/UV light exposure) and regional rates of ADHD. One study examined three large datasets across 49 U.S. states for 2003 and 2007, and across 9 non-U.S. countries. This study examined the prevalence of ADHD and Solar Intensity (SI) maps. They found an inverse association between solar intensity and prevalence of ADHD. Another study examined two national survey datasets. They found an inverse relationship between altitude and prevalence of ADHD. Investigators hypothesize, as suggested by Huber, that a common denominator on the above studies is the increased vitamin D levels in those exposed to a higher solar intensity, which is known to increase with altitude.

Clinical Study Identifier: NCT03103750

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