Subgroup analysis of study design, type of PTSD assessed and quality characteristics in the Meta-Analysis of 5-HTTLPR polymorphisms and Post-traumatic Stress Disorder (PTSD) in the biallelic approach.

‡K: Number of studies; #Number of alleles S or L duplicates the number of participants as each participant has two alleles (S, L or one of each one); OR: Odds Ratio; 95% CI: 95% Confident Interval; & Chi-squared test for subgroup differences; NA: Not applicable; †HWE: Hardy-Weinberg Equilibrium.