We used the tri-allelic 5-HTTLPR genotype, the methods for which are described in detail in Kranzler et al. (2011). Briefly, we first differentiated the S and L alleles. Then, LA vs. LG allele-specific probes were used to characterize the A→G SNP in the L allele. The LG and S alleles were grouped together and designated as S′ (the lower expression allele) and the LA allele was designated as L′ (the higher expression allele). As reported in Kranzler et al. (2011), genotype frequencies did not differ from Hardy-Weinberg equilibrium expectations. We limited the analysis to two genotype groups because of the small sample sizes.
