Major depressive disorder and the 5-HTTLPR in Spanish and Mexican populations

Preliminary evidence of an increased risk of suffering from MDD for individuals carrying the 5HTTLPR S allele was described in 70 Spanish patients [1]. The present study aimed to analyze the potential relevance of the 5-HTTLPR genotypes and the risk of suffering from MDD in Mexicans and Spaniards. One hundred and twenty-two (70 previously analyzed) white Spanish and 101 Mexican Mestizo patients with a diagnosis of MDD (DSM-IV) were studied. Additionally, 327 Spaniards and 153 Mexican Mestizo healthy volunteers were also studied by a previously reported PCR method [1]. Genotypes and allele frequencies were compared between MDD patients and HVs by two-tailed Fisher's test. The frequencies of 5HTTLPR LL, LS and SS genotypes in the Spanish population (MDD vs. HV) were 19.7 vs. 28.8%, 54.9 vs. 50.5% and 25.4 vs. 19.9 %. In the Mexican Mestizo population the frequencies in the MDD vs. HV groups were 14.9 vs. 18.3%, 49.5 vs. 55.6%, and 35.6 vs. 26.1% for 5HTTLPR LL, LS, and SS genotypes, respectively. The frequencies of 5-HTTLPR genotypes of the four groups (MDD and HV from Spain and Mexico) corresponded to those predicted by the Hardy–Weinberg law. The odds ratio associated with the 5-HTTLPR-S allele were 1.72 (95% CI: 1.04-2.85) and 1.28 (95% CI: 0.64-2.55) for the MDD in comparison with the HV group in Spaniards and Mexicans, respectively. The frequency of S was higher than the frequency of L allele in both MDD groups. In the Spanish population, the S allele was significantly higher (p<0.05) in MDD (52.9%) than in HV (45.1%). However, in the Mexican Mestizo population, the S allele was higher in the MDD group (60.4%) compared to HV (53.9%), but this difference was not significant. Moreover, the frequency of 5-HTTLPR-S allele in the Spanish HV (45.1%) was higher (p<0.05) than Mexican Mestizo HV (53.9%). The S allele of 5HTTLPR is related to risk of MDD in both populations. In addition, we have found differences in the frequency of 5-HTTLPR-S allele between Spaniards and Mexican Mestizo populations.

Grants: Supported by grants from the Spanish Ministry of Health Instituto de Salud Carlos III and EU-FEDER PI10/02758, CP06/00030 (PD); AEXCID (9IA006) Junta de Extremadura and EU-FEDER (BS10023) and Consejo Nacional de Ciencia y Tecnología de México (Nº 59366). This work was coordinated by Network Red Iberoamericana de Farmacogenética y Farmacogenómica (CYTED206RT0290).

References:

1. Dorado P, Penas-Lledo EM, Gonzalez AP, Caceres MC, Cobaleda J, Llerena A. Fundam Clin Pharmacol 2007;21:451-3. Bulletin of Clinical Psychopharmacology 2011;21(Suppl. 2):S185-6