Association of Brain-Derived Neurotrophic Factor G196A and Attempted Suicide: A Case-Control Study in Rural China

Association of NTRK2 gene with suicidality: a meta-analysis

BACKGROUND

Previous studies have shown that genes in brain development pathways may have important roles in affecting risk of suicidal behaviors, with our previous meta-analysis supporting a role of the brain-derived neurotrophic factor (BDNF) gene. NTRK2 is a gene that encodes the neurotrophic receptor tyrosine kinase 2, which is a receptor for BDNF. In the current study, we aim to examine the potential association between NTRK2 single nucleotide polymorphism (SNPs) and suicidal ideation/behaviors.

METHODS

We first conducted a literature search using keywords like 'NTRK2', 'TRKB', and 'suicid*' to identify papers on NTRK2 SNPs and suicidal ideation/behaviors. In addition, we have individual-level genotype data for all the identified SNPs in literature search. We used the R meta package to perform meta-analyses on both the genotype count and the allele count data. Moreover, we performed meta-analyses on specific haplotypes within each haplotype block.

MAIN RESULTS

Following our literature search and meta-analyses on 20 NTRK2 SNPs across up to 8467 samples, we found three SNPs, rs10868235 [N = 5,318, odds ratio (OR) = 1.34, P = 0.02], rs1867283 (N = 5,134, OR = 0.73, P = 0.04), and rs1147198 (N = 5,132, OR = 1.36, P = 0.03) to be nominally associated with suicidal attempts. Those three findings, however, did not survive multiple-testing corrections. Also, none of the haplotype blocks showed significant involvement in suicidality.

CONCLUSION

Our results suggest that the NTRK2 gene may not have a major role in suicidality. Future efforts, however, should explore gene-gene interaction and pathway analyses.

Risk and Protective Factors for Childhood Physical Abuse and Suicidal Ideation: The Effect of Brain-Derived Neurotrophic Factor Polymorphism and Social Support

OBJECTIVE

This study aimed to explore the relationship between childhood physical abuse and suicidal ideation considering the effects of genetic and environmental factors in patients with post-traumatic stress disorder (PTSD) by focusing on brain-derived neurotrophic factor (BDNF) polymorphism and social support, respectively.

METHODS

One-hundred fourteen patients with PTSD and 94 healthy controls (HCs) were genotyped with respect to BDNF Val66Met polymorphism. All participants underwent psychological assessments. The hierarchical regression analysis and the simple slope analysis were conducted.

RESULTS

As for patients with PTSD, the moderation effect of BDNF polymorphism was significant but not for social support. Specifically, the BDNF Val/Val genotype worked as a risk factor and strengthens the relationship between childhood physical abuse and suicidal ideation. As for the HCs, the significant moderation effect was found only in social support, but not for BDNF polymorphism. The relationship between childhood physical abuse and suicidal ideation was weakened for the HCs with high social support.

CONCLUSION

This study demonstrated a significant BDNF genetic vulnerability for suicide in patients with PTSD who experienced childhood physical abuse. Our results suggested that social support provided a mitigating effect on the relationship between childhood physical abuse and suicidal ideation only in the HCs.

Association of Brain-Derived Neurotrophic Factor rs6265 G>A polymorphism and Post-traumatic Stress Disorder susceptibility: A systematic review and meta-analysis

BACKGROUND

Previous studies have shown that the brain-derived neurotrophic factor (BDNF) rs6265 G > A polymorphism is closely related post-traumatic stress disorder (PTSD) risk. However, the results were not consistent. We therefore conducted a meta-analysis to explore the underlying relationships between BDNF rs6265 G > A polymorphism and PTSD risk.

MATERIALS AND METHODS

Five online databases were searched, and all related studies were reviewed up to July 1, 2020. Odds ratios (ORs) and corresponding 95% confidence intervals (CIs) were calculated to examine the statistical power of each genetic model. In addition, heterogeneity, sensitivity accumulative analysis, and publication bias were examined to check the statistical power.

RESULT

Overall, 16 publications involving 5,369 subjects were included in this systematic review and 11 case-control studies were analyses in meta-analysis. The pooled results indicated an increasing risk of A allele mutations with PTSD risk. Moreover, the sequential subgroup analysis also demonstrated some similar situations in Asian populations and other groups.

CONCLUSION

Current meta-analysis suggests that the BDNF rs6265 G > A polymorphism might be involved in PTSD susceptibility.

The rs6265 Polymorphism of the BDNF Gene Is Related to Higher-Lethality Suicide Attempts in the Korean Population

OBJECTIVE

Since the risk of suicide cannot be predicted by clinical symptoms alone, and suicide is known to have a genetic component, the discovery of genetic markers that can predict the lethality of suicide attempts is a clinically important topic. There have been many studies aiming to determine whether the rs6265 polymorphism of the BDNF gene is associated with suicidality; however, the results have been mixed, and there have been few studies investigating the relationship between this polymorphism and suicide attempt lethality.

METHODS

We assessed suicide lethality in 258 individuals who had attempted suicide using the relative risk ratio (RRR) scale and by genotyping the rs6265 polymorphism of the BDNF gene.

RESULTS

The RRR score for suicide attempts was higher in subjects with Met/Val and Val/Val genotypes than in that with a Met/Met genotype (p=0.015). The RRR score for suicide attempts was also higher in Val allele carriers (Met/Val+Val/Val) than in Met/Met homozygotes (p=0.006).

CONCLUSION

This study demonstrates the possibility that the rs6265 polymorphism of the BDNF gene could be used as a genetic marker to predict the lethality of suicide attempts, but more replication studies are needed for the application of this result in clinical practice.

An examination of genes, stress and suicidal behavior in two First Nations communities: The role of the brain-derived neurotropic factor gene

Suicide claims over 800,000 lives each year worldwide. Suicide rates in indigenous populations in Canada are about double that of the national average, making it a serious public health issue. Numerous factors are involved in suicide risk, including genetic factors, as well as various psychosocial stressors, such as historical experience with the Indian Residential School system for Indigenous populations, as well as protective variables such as social support. Here, we report the first genetic study of suicidal behaviors that includes multiple measures of stress and social supports. We investigated the role of the functional Val66Met marker (rs6265) in the Brain-Derived Neurotropic Factor (BDNF) gene in suicidal ideation and suicide attempt in a First Nations community sample (N = 278). We did not find a significant association between the BDNF rs6265 marker and suicidal behaviors. We found childhood adversities, recent life stress, chronic stress, perceived stress, difficulties, and hazardous alcohol use to be associated with both suicidal ideation and suicide attempt. Thus, while additional studies with larger samples are required to elucidate the genetic component of suicide, addressing environmental stressors may be important for suicide prevention.

Brain derived neurotrophic factor (BDNF) and suicidal behavior: A review of studies from Asian countries

The biological basis of suicide and suicidal behavior is actively researched. Recently, the role of Brain Derived Neurotropic Factor (BDNF) in suicidal behavior has gained attention and significant results are observed. In this review, we aimed to focus on the studies from Asian countries that have explored the role of BDNF and suicidal behavior. The review highlights the findings from these studies and discusses the possible avenues that should be explored in future studies from Asian countries to understand more on suicidal behavior and possible prevention.

Exploring the association between BDNF Val66Met polymorphism and suicidal behavior: Meta-analysis and systematic review

Suicide is a serious worldwide health problem of critical consequences. Nowadays genetic factors are considered to be an important cause of suicide. The association between Val66Met (rs6265) polymorphism of the BDNF gene and suicide behavior has been increasingly studied. The aim of this study was to perform a meta-analysis in order to unravel the possible association between BDNF gene Val66Met polymorphism and suicide behavior. These meta-analysis and systematic review were performed using 23 articles that searched for a genetic association between Val66Met and suicide behavior, including 4532 cases and 5364 control subjects. The association was analyzed following the models: allelic, homozygous, heterozygous, dominant and recessive. Also, analyses by ethnicity (Caucasian and Asian populations) were done following the same four models. When the overall population was evaluated, we found no evidence of association between the polymorphism Val66Met of BDNF (rs6265) and suicide behavior (Met vs. Val: OR: 1.01; 95% CI = 0.92-1.10). However, a significant increased risk was found in the subgroup analysis by ethnicity in Caucasian populations (Met-Met vs. Met-Val + Val-Val: OR: 1.96; 95% CI = 1.58-2.43) and Asian populations (Val-Val vs. Val-Met + Met: OR: 1.36; 95% CI = 1.04-1.78). Our results suggest there is no association between the BDNF gene Val66Met (rs6265) and suicide behavior in the overall population. However, ethnic differences can be observed and the BDNF Val66Met might increase the risk for suicide behavior in Asian and Caucasian populations. Further studies with larger samples are necessary in order to have conclusive outcomes.

Characteristics of suicide completers and attempters in rural Chinese population

OBJECTIVE

This study aimed to compare the similarities and differences between suicide completers and attempters in rural China.

METHODS

Two paired case-control studies of completed suicide and suicide attempts were conducted in rural Shandong, China. This analysis included 409 suicide attempters (SA) with a mean age of 43.90 (SD=13.31), 117 suicide completers (SC) with a mean age of 50.38 (SD=13.02) and their controls matched by gender, age (within 3years), and residence. Logistic regression models were used to examine risk factors of suicide attempts and completed suicide and the differences between SA and SC.

RESULTS

Compared to their matched controls, suicide attempters and completers shared the following common risk factors: low levels of education (middle school or under) (OR, 95% CI: 2.79, 1.40-5.55 for SA and 16.98, 1.59-181.60 for SC), negative life events (OR, 95% CI: 7.37, 4.73-11.50 for SA and 21.08, 4.74-93.71 for SC), and mental disorders (OR, 95% CI: 7.52, 3.85-14.69 for SA and 22.39, 2.65-189.60 for SC). Compared to suicide attempts, completed suicide was associated with the following risk factors: male gender (OR, 95% CI: 1.75, 1.06-2.90), advancing age (OR, 95% CI: 1.02, 1.00-1.04), poor family economic status (OR, 95% CI: 6.74, 3.22-14.13), prior suicide attempts (OR, 95% CI: 2.43, 1.18-4.97), family suicide history (OR, 95% CI: 2.59, 1.33-5.06), high suicide intent (OR, 95% CI: 1.15, 1.05-1.27), and highly lethal methods (OR, 95% CI: 13.65, 6.51-28.59).

CONCLUSIONS

Although suicide completers and attempters share some common risk factors, suicide completers are more likely to have prior suicide attempts, family suicide history, and higher suicidal intent, and to use highly lethal methods in rural Chinese.