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Attention deficit hyperactivity disorder (ADHD) is a developmental disorder characterized by poor focus, hyperactivity, and impulsive behavior. Approximately 5 percent of all children worldwide have ADHD. Findings from a recent study suggest that poor maternal vitamin D status may play a role in the pathophysiology of ADHD in children.
Vitamin D is a fat-soluble vitamin stored in the liver and fatty tissues. It plays key roles in several physiological processes, such as the regulation of blood pressure, calcium homeostasis, immune function, and the regulation of cell growth. Emerging evidence indicates that vitamin D is critical for the health and function of the central nervous system. Vitamin D is synthesized in a multistep process in the skin, liver, and kidneys following exposure to ultraviolet light or it can be obtained from dietary sources such as salmon, mushrooms, and many fortified foods.
The National Academy of Medicine (formerly the Institute of Medicine, IOM) has determined that people are at risk for vitamin D deficiency if their levels are less than 30 nmol/L, and are potentially at risk for deficiency if their levels are between 30 and 50 nmol/L. Levels of 50 nmol/L are considered sufficient for most people.
The population-based case-control study included 1,067 children born in Finland between 1998 and 1999 who had been diagnosed with ADHD and 1,067 matched controls. The study drew on data from Finnish national registries as well as maternal blood samples collected during the first trimester of pregnancy for women enrolled in the Finnish Maternal Cohort of the Northern Finland Biobank Borealis. These samples were collected before Finland began recommending vitamin D supplementation during pregnancy.
The data were adjusted for several potential confounding factors, including the number of previous births, maternal socioeconomic status, maternal age, self-reported smoking during pregnancy, maternal cotinine levels (a biomarker of nicotine), gestational age, weight for gestational age, information on maternal and paternal psychiatric diagnoses (including ADHD), substance use disorders, maternal immigrant background, and month of blood draw.
The study revealed that children born to women who had low vitamin D status during their pregnancies were 45 percent more likely to develop ADHD, even after adjusting for maternal socioeconomic status and age. The average vitamin D level among women whose children developed ADHD was 29 nmol/L.
There are biologically plausible explanations for the association between developmental vitamin D deficiency and an increased risk of offspring ADHD. Early pregnancy is a critical period for fetal brain development, which is a complex process influenced by genetics and the in utero environment.
I published an article a few years ago first identifying how vitamin D regulates the conversion of the essential amino acid tryptophan into serotonin, and how this may influence the development of neurodevelopmental disorders such as autism spectrum disorder, ADHD, bipolar disorder, and schizophrenia, which all share as a unifying attribute low brain serotonin. Read more about these findings here.