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Cognitive impairments are known to be core features in psychotic disorders. Previous studies have suggested a link between low vitamin D levels and cognitive dysfunction in the elderly, but few studies have assessed vitamin D levels in younger populations or in persons with a psychotic disorder.
For the current cross-sectional study, Mari Nerhus, M.D., Ph.D., of the Norwegian Centre for Mental Disorders Research and colleagues recruited 225 patients (mean age 30 years) with a DSM-IV psychotic disorder from South Norway between May 2003 and September 2014, and 159 healthy controls. The participants underwent a clinical assessment, a physical examination where vitamin D was assessed, and two different cognitive test batteries. Multiple regression models were performed to evaluate the effect of vitamin D deficiency on key cognitive domains, including processing speed, verbal learning, verbal memory, and executive functioning (verbal fluency, working memory, inhibition, and set-shifting).
The study found vitamin D deficiency was significantly associated with decreased processing speed and decreased fluency when the results were controlled for age, ethnicity, IQ, patient versus control status, and substance or alcohol abuse.
Although larger randomized, controlled trials are necessary to determine the potential beneficial effects of vitamin D on cognition in psychotic disorders, the authors noted “vitamin D is considered safe to use, is well tested, and is readily available.”
They concluded, “These benefits, combined with the substantial negative effects of cognitive dysfunctions on daily living are good arguments for planning large-scale randomized, controlled studies in target populations to reach conclusions about the potential beneficial effect of vitamin D on cognition in psychotic disorders.”
For related information, see the Psychiatric News article “Could Cognitive Assessments Enhance Ability to Detect Transition to Psychosis?”
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