Risk factors and peripheral biomarkers for schizophrenia spectrum disorders : an umbrella review of meta-analyses

Objective: This study aimed to systematically appraise the meta-analyses of observational studies on risk factors and peripheral biomarkers for schizophrenia spectrum disorders. Methods: We conducted an umbrella review to capture all meta-analyses and Mendelian randomization studies that examined associations between non-genetic risk factors and schizophrenia spectrum disorders. For each eligible meta-analysis, we estimated the summary effect size estimate, its 95% confidence and prediction intervals and the I2 metric. Additionally, evidence for small-study effects and excess significance bias was assessed. Results: Overall, we found 41 eligible papers including 98 associations. Sixty-two associations had a nominally significant (P-value