Serum 25-hydroxyvitamin D levels and the risk of depression: a systematic review and meta-analysis

No quantitative systematic review or meta-analysis of population-based epidemiological studies has been conducted to assess the association between serum 25-hydroxyvitamin D (25(OH)D) levels and the risk of depression. This study aimed to summarize the current evidence from cross-sectional and prospective cohort studies that have evaluated the association between 25(OH)D levels and the risk of depression.

Relevant studies were identified by systematically searching the PubMed, EMBASE, Web of Science, and PsycINFO databases through April 2012. Cross-sectional and cohort studies that reported adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for the association of interest were included. The reported risk estimates for 25(OH)D categories were recalculated, employing a comprehensive trend estimation from summarized dose-response data. A pooled OR was calculated separately for cross-sectional and cohort studies using random-effects models.

In the meta-analysis, 25(OH)D levels were significantly inversely associated with depression in 5 of 11 case-control studies and 2 of 5 cohort studies. The pooled estimate of the adjusted OR of depression in 11 cross-sectional studies (n = 43,137) was 0.96 (95% CI = 0.94-0.99, I2 = 63%) for a 10 ng/ml increase in 25(OH)D levels. The 5 included cohort studies comprised 12,648 participants, primarily elderly individuals, whose serum 25(OH)D levels were measured, and 2,663 experienced depression events during follow-up. The pooled adjusted OR of depression was 0.92 (95% CI = 0.87-0.98, I2 = 50%) for a 10 ng/ml increase in 25(OH)D levels.

Our results indicate an inverse association between serum 25(OH)D levels and the risk of depression. Further studies are warranted to establish whether this association is causal.