(a).
| Author | Title | Year | Country | Objective | Sample size | BDNF genetic variant | Genotypic frequency (Val/Val) | Laboratorial method | Results | p value (case vs. control) | Odds ratio |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Peters et al. [18] | BDNF Val66Met polymorphism and resilience in major depressive disorder: the impact of cognitive psychotherapy | 2020 | Brazil | Investigate the BDNF Val66Met polymorphism effect on MDD patients' resilience scores and response to cognitive therapy. |
n = 106 F = 83 (78.3%) M = 23 (21.7%) |
rs6265 | 77.4% (n = 82) | TaqMan | The BDNF Val66Met polymorphism may be related to resilience in MDD patients. | 0.214 | — |
| Brunoni et al. [19] | Association of BDNF, HTR2A, TPH1, SLC6A4, and COMT polymorphisms with tDCS and escitalopram efficacy: ancillary analysis of a double-blind, placebo-controlled trial | 2020 | Brazil | Investigate whether the proposed SNPs correlate with neuroplasticity and if monoamine neurotransmitters activity is associated with the transcranial direct current stimulation (tDCS) effectiveness in MDD. |
n = 195 F = 132 (67.7%) M = 63 (32.3%) |
rs6265 | 65.1% (n = 127) | MassARRAY SNP genotyping | The A (Met) allele did not affect depression symptom improvement in any of the treatments: placebo (p = 0.84), tDCS (p = 0.48), nor escitalopram (p = 0.98). | 0.78 | — |
| Aldoghachi et al. [20] | Screening of brain-derived neurotrophic factor (BDNF) single nucleotide polymorphisms and plasma BDNF levels among Malaysian major depressive disorder patients | 2019 | Malaysia | Determine the association of three BDNF variants (rs6265, rs1048218, and rs1048220) in MDD patients |
n = 300 F = 203 (67.7%) M = 97 (32.3%) |
rs6265, rs1048218, rs1048220 | 24.3% (n = 73) | PCR and sequencing | The A (Met) allele increases the risk of developing MDD in the Malaysian population. | 0.0075∗ | 1.95 |