Low vitamin D status and suicide: a case-control study of active duty military service members.

Considering that epidemiological studies show that suicide rates in many countries are highest in the spring when vitamin D status is lowest, and that low vitamin D status can affect brain function, we sought to evaluate if a low level of 25-hydroxyvitamin D [25(OH)D] could be a predisposing factor for suicide.We conducted a prospective, nested, case-control study using serum samples stored in the Department of Defense Serum Repository. Participants were previously deployed active duty US military personnel (2002-2008) who had a recent archived serum sample available for analysis. Vitamin D status was estimated by measuring 25(OH) D levels in serum samples drawn within 24 months of the suicide. Each verified suicide case (n = 495) was matched to a control (n = 495) by rank, age and sex. We calculated odds ratio of suicide associated with categorical levels (octiles) of 25(OH) D, adjusted by season of serum collection.More than 30% of all subjects had 25(OH)D values below 20 ng/mL. Although mean serum 25(OH)D concentrations did not differ between suicide cases and controls, risk estimates indicated that subjects in the lowest octile of season-adjusted 25(OH)D (<15.5 ng/mL) had the highest risk of suicide, with subjects in the subsequent higher octiles showing approximately the same level of decreased risk (combined odds ratio compared to lowest octile = 0.49; 95% C.I.: 0.315-0.768).Low vitamin D status is common in active duty service members. The lowest 25(OH)D levels are associated with an increased risk for suicide. Future studies could determine if additional sunlight exposure and vitamin D supplementation might reduce suicide by increasing 25(OH) D levels

Results of the conditional logistic regression analysis not including covariates.

1<p>Octiles were calculated from waveform adjusted 25(OH)D levels based on the distribution of the control subjects. Cutoff 25-hydroxyvitamin D values were as follows. octile 1: ≤15.5; octile 2: 15.6–18.8; octile 3: 18.9–21.2; octile 4: 21.3–22.9; octile 5: 23.0–25.4; octile 6: 25.5–29.2; octile 7: 29.3–36.0; octile 8: >36.0.</p