Association of Vitamin D with Suicide Behaviors: A Systematic Review and Meta-Analysis.

Objective: Research findings on the relationship between vitamin D and suicide are not consistent; therefore, the objective of the present paper is to assess the relationship between vitamin D and suicide behaviors using a systematic review and meta-analysis. Method : A search strategy was developed using keywords including "Vitamin D", "Vitamin D deficiency", "suicide" "attempted suicide", "completed suicide", "Suicide, Attempted", "Suicidal Ideation." We searched databases including Scopus, Medline, Web of Science, and Google Scholar by July 7, 2022. We examined the titles, abstracts, and full texts of the articles to select eligible ones. To pool the results of the selected studies, we used the random-effect method and mean difference as the effect size. The quality of the articles was evaluated by the Newcastle-Ottawa Scale (NOS). Moreover, heterogeneity and bias of reporting were evaluated by the I² statistic and Egger's and Begg's tests, respectively. Results: Out of 149 studies retrieved in the databases, 11 studies were included in the final phase. Among these, the pooled findings of seven studies included in the meta-analysis phase showed that low levels of vitamin D are related to increased probability for suicide behaviors (P < 0.05). Moreover, subgroup analysis showed a significant relationship between vitamin D and suicide ideation and suicide attempt (P < 0.05). In addition, the I² statistic indicated moderate heterogeneity (58%) and Egger's and Begg's tests did not show any evidence of publication bias (P > 0.05). Conclusion: This study provides evidence in favor of the relationship between vitamin D and suicide behaviors. It suggests that insufficient levels of vitamin D play a role in suicidal behaviors. However, it should be noted that further and stronger evidence is needed to establish this role. Finally, incorporating vitamin D-rich foods into the diet or taking vitamin D supplements is recommended to reduce the risk of suicide.