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Vitamine D en de mentale gezondheid*
Uit een kleine Amerikaanse studie blijkt dat kinderen met mentale problemen vaak een duidelijk vitamine D te kort hebben, zeker als de problemen van psychotische aard zijn. 61% van de kinderen had een tekort aan vitamine D (bloedwaarden < 30 ng/ml) waarvan 21% zelfs waarden < 20 ng/ml. Dit laatste was bij hen met problemen van psychotische aard zelfs 43%. Uit recente studies blijkt volgens de onderzoekers dat lage bloedwaarden vitamine D gerelateerd zijn aan psychiatrische aandoeningen, inclusief depressies, schizofrenie en bipolaire stoornissen.
Low Vitamin D: A Contributor to Mental Disorders in Children?
Children with severe mental health disorders, including psychosis, have twice the rate of vitamin D insufficiency as mentally healthy children, new research suggests.
A study presented here at the American Psychiatric Association Annual Meeting by investigators at the Oregon Health & Science University in Portland showed 21% of children with severe psychiatric symptoms requiring residential care had serum 25-hydroxyvitamin D (25[OH]D) levels lower than 20 ng/mL (the American Academy of Pediatrics [AAP] minimum recommended level) compared with 14% of children who were participants in the National Health and Nutrition Examination Survey III (NHANES III), a population-based study designed to assess the health and nutritional status of children and adults in the United States.
"That is 50% more than children in a normal population, so based on our findings this means that 1 out of 5 kids with severe mental illness has low vitamin D levels," principal investigator Keith Cheng, MD, told Medscape Medical News.
"The prevalence of vitamin D deficiency (43%) was most common in children with psychotic disorders compared to other mental health disorders," said first study author Mini Zhang, MA.
Vitamin D insufficiency is associated with a range of adverse medical outcomes, most commonly endocrine function and bone health, but more recently has also been linked to a variety of other medical conditions, including gastrointestinal disorders, asthma, cancer, and diabetes, added Ms. Zhang.
Furthermore, she said, recent research has linked low vitamin D levels to the development of psychiatric disorders, including depressive symptoms, schizophrenia, and bipolar disorder.
In addition, there is a controversial hypothesis by researcher John Cannell, MD, who heads The Vitamin D Council, a nonprofit educational group, that vitamin D deficiency is linked to autism.
No Definitive Data 
"So there are various studies that show some correlation between [low] vitamin D and mental illnesses, but the data out there are not consistent enough, or the evidence is not strong enough, for us to draw definitive conclusions. Our research was an attempt to try and fill in a piece of this puzzle and perhaps prompt future studies that will examine this relationship further," Ms. Zhang told Medscape Medical News.
The retrospective medical record review included 67 patients (29 female and 38 male) with an age range of 7 to 17 years from 2 Oregon residential psychiatric programs who had serum 25(OH)D levels evaluated.
There were 1 to 5 psychiatric diagnoses documented per patient. Individual diagnoses were organized into 6 diagnostic categories, including anxiety disorder, autism, disruptive disorder, mood disorder, psychotic disorder, and other, which was defined as any psychiatric diagnosis that did not fit into the other 5 categories.
All diagnoses for each category were counted to calculate the percentage of diagnostic categories that met hypovitaminosis D cutoff values. Deficiency was defined as serum 25(OH)D levels below 20 ng/mL, and insufficiency was defined as blood levels below 30 ng/mL as used by local laboratories in the study, the investigators report.
The overall mean 25(OH)D level in the study population was 28.91 ng/mL, which was classified as insufficient. Vitamin D levels in 21% of patients were below 20 ng/mL, compared with 14% in the NHANES study. Two-thirds of patients (61%) fell below the cutoff value of 30 ng/mL.
With a mean (SD) of 26.47 (12.42) ng/mL, investigators report that patients with psychotic disorders had the lowest mean level of serum 25(OH)D and, at 43%, the highest prevalence of vitamin D deficiency.
Need for Standardization 
Dr. Cheng said the key take-home message from this study is that clinicians should have a high index of suspicion for low vitamin D levels in children with mental disorders and test for it. This may be particularly important in children with psychotic or mood disorder symptoms, he added.
"Low vitamin D is so easily diagnosed that overlooking it may represent a missed opportunity. Psychiatric diagnoses are often not as clear-cut as many other [medical] illnesses where you can get a lab value or an imaging test and based on the results make a definitive diagnosis. But with low vitamin D you can get a number, and it is pretty easy to diagnose and treat," he said.
"We're still not entirely certain of the role vitamin D plays in brain function and development, but we do know there are vitamin D receptor sites in various brain cells. We don't know exactly what happens when those receptor sites aren't active, but we do know they are there and that they are there for a reason," Dr. Cheng added.
Both Ms. Zhang and Dr. Cheng noted that there is no standardized cutoff level for vitamin D deficiency, which can create confusion for clinicians. For instance, local laboratories in this study defined vitamin D insufficiency serum levels below 30 ng/mL. In contrast, they note the AAP defines deficiency as levels below 20 ng/mL.
"Defining what constitutes vitamin D deficiency was one of the very challenging parts of this study and others. There is controversy about this all over the place. Some studies say 15 [ng/mL], some say 20, some say 30, some say 32. There really needs to be a standardized cutoff level," said Ms. Zhang.
"What we are recommending right now is just to follow the AAP and the Institute of Medicine cutoff value, which uses 20 ng/mL," said Dr. Cheng.
Call for More Research 
Commenting on the study for Medscape Medical News, David Fassler, MD, clinical professor of psychiatry, University of Vermont in Burlington, said the findings raise "interesting questions regarding the etiology of the deficiencies identified and the possible relationship with specific psychiatric symptoms and/or disorders.
"However, the design of the current study precludes such analyses. I would concur with the authors' conclusion that the findings warrant further research with a larger sample and more stringent diagnostic criteria," said Dr. Fassler.
Dr. Cheng acknowledged that the retrospective nature of the study is a major limitation and added that he hopes to conduct prospective research into this issue in a study that compares vitamin D levels in psychiatric outpatients, inpatients, and healthy controls.
The study authors and Dr. Fassler have disclosed no relevant financial relationships. 
American Psychiatric Association (APA) Annual Meeting: NR01-67. (Januari 2012)