Major Depression Episodes: Do Low Levels of Vitamin D Affect Cognition?
Cognitive function should be a focus when evaluating the therapeutic effect of vitamin D for patients experiencing a major depressive episode.
Patients with major depressive episodes (MDE) who also have hypovitaminosis D (hypo VD, defined as 250 hydroxyvitamin D level <50 nmol/L) are more prone to cognitive inhibition than individuals with MDE and normal vitamin D levels, according to a study published in the Journal of Affective Disorders.1
Raoul Belzeaux, MD, PhD, faculty in the department of psychiatry, McGill University in Montreal, Canada, and colleagues conducted a cross-sectional study including 91 patients aged 18 to 65 (mean age, 38.5; 65.9% women) with a diagnosis of major depressive disorder (MDD) and presenting with MDEs at the time of inclusion. The mean level of depression assessed using the 21-item Hamilton Rating Scale (HAMD-21) was 32.6 on a 0 to 50 scale (standard deviation, 6.0; range, 21-48).
Cognitive inhibition was evaluated by a neuropsychologist using the Stroop Color Test, the Trail Making Test (to assess visual attention and task switching), and the Hayling Sentence Completion Test (to assess executive functioning). The researchers also assessed decision-making with the Iowa Gambling Task, verbal fluency, working memory with the Digit Span Test, and verbal IQ with the National Adult Reading Test.
Patients with hypo VD (n=28) had their first MDE at a later age than study participants with no hypo VD (n=63), with age of onset at 38.2 ± 12.7 vs 31.6 ± 10.5 (P =.012). The only test that showed a significant difference between the 2 groups was the Stroop interference test for which patients with hypo VD had a higher index time compared with patients without hypo VD (66.6±29.5 vs 53.0±26.3; P =.047).
Logistic regression analysis indicated an association between a high Stroop interference time index and hypo VD, after controlling for other possible confounding variables (including age, gender, age of first MDE, and depression severity; P =.025).
The authors conclude that this study indicates an association between cognitive inhibition and hypo VD and add that these results “may have interesting consequences leading to more precise phenotypic description and classification of MDE.”
Study limitations include limited sample size; lack of causal relationship between cognitive function and hypo VD in interventional studies; and dietary or physical activity differences that may have affected both depressive symptoms and VD levels.
Belzeaux R, Annweiler C, Bertrand JA, et al. Association between hypovitaminosis D and cognitive inhibition impairment during major depression episode. J Affect Disord. 2018;225:302-305.