5-HTTLPR short allele, resilience, and successful aging in older adults

Genetic Variants Associated With Resilience in Human and Animal Studies

Resilience is broadly defined as the ability to maintain or regain functioning in the face of adversity and is influenced by both environmental and genetic factors. The identification of specific genetic factors and their biological pathways underpinning resilient functioning can help in the identification of common key factors, but heterogeneities in the operationalisation of resilience have hampered advances. We conducted a systematic review of genetic variants associated with resilience to enable the identification of general resilience mechanisms. We adopted broad inclusion criteria for the definition of resilience to capture both human and animal model studies, which use a wide range of resilience definitions and measure very different outcomes. Analyzing 158 studies, we found 71 candidate genes associated with resilience. OPRM1 (Opioid receptor mu 1), NPY (neuropeptide Y), CACNA1C (calcium voltage-gated channel subunit alpha1 C), DCC (deleted in colorectal carcinoma), and FKBP5 (FKBP prolyl isomerase 5) had both animal and human variants associated with resilience, supporting the idea of shared biological pathways. Further, for OPRM1, OXTR (oxytocin receptor), CRHR1 (corticotropin-releasing hormone receptor 1), COMT (catechol-O-methyltransferase), BDNF (brain-derived neurotrophic factor), APOE (apolipoprotein E), and SLC6A4 (solute carrier family 6 member 4), the same allele was associated with resilience across divergent resilience definitions, which suggests these genes may therefore provide a starting point for further research examining commonality in resilience pathways.

A Re-evaluation of Candidate Gene Studies for Well-Being in Light of Genome-Wide Evidence

Ever since twin-family studies found that a substantial amount (± 40%) of the variation in well-being can be explained by genetic variation, several candidate genes have been proposed explaining this variation. However, these candidate gene and candidate gene-by-environment interaction studies have been surrounded by controversy regarding the validity and replication of their results. In the present study, we review the existing candidate gene literature for well-being. First, we perform a systematic literature search that results in the inclusion of 41 studies. After describing the results of the included studies, we evaluated the included candidate polymorphisms by (1) looking up the results for the studied candidate SNPs in a large well-being genome-wide association study, (2) performing association analyses in UK biobank (UKB) data for the candidate variable number tandem repeats (VNTR) and the APOE ε4 allele, and (3) studying possible candidate interactions with positive and negative environmental moderators using UKB data. We find no support for any of the candidate genes or candidate gene-environment interactions for well-being, with the exception of two SNPs that were chosen based on genome-wide evidence. While the generalizability of our findings is limited by our phenotype and environment definitions, we strongly advise well-being researchers to abandon the candidate gene approach in the field of well-being and move toward genome-wide approaches.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s10902-022-00538-x.

Association between resilience and a functional polymorphism in the serotonin transporter (SLC6A4) gene: A meta-analysis

Resilience is a mechanism used by humans to adapt to adverse situations. It is a protective factor against mental health problems. This process can be influenced by environmental and genetic factors. Several genes have been associated with interindividual differences in resilience levels, but the results are inconclusive. Therefore, the aim of this meta-analysis was to evaluate the effect of a functional polymorphism (5-HTTLPR) in the SLC6A4 gene on resilience levels. A search in PubMed, HugeNavigator and Google Scholar databases was carried out and 16 studies about the association of 5-HTTLPR polymorphism and resilience in humans were identified. The OpenMeta[Analyst] program was employed to perform statistical analysis using a random-effects model. The final analysis included 9 studies, for a total of 4,080 subjects. Significant results were found when the standardized mean differences (SMD) of LL and SL carriers were compared, (SMD: -0.087 (confidence interval: -0.166 to -0.008; I²: 0 %); P value: 0.031). A significant result was also found in an analysis comparing SS/SL versus LL genotypes (SMD: -0.231; confidence interval: -0.400 to -0.061, P value: 0.008; I²: 0 %). This is the first meta-analysis performed to identify the pooled association of a functional polymorphism in the serotonin transporter gene and resilience. The current results suggest that the L/L genotype is associated with resilience. Further studies are necessary to elucidate the role of genetics on the resilience mechanisms.

Influence of psychosocial stress on activation in human brain regions: moderation by the 5-HTTLPR genetic locus

Variants of the serotonin transporter linked polymorphic region (5-HTTLPR) of the serotonin transporter gene SLC6A4 have been related with the onset of depression, anxiety, and other mental disorders. Homozygotes for the short 5-HTTLPR variant, referred to as the SS genotype, have greater cortisol responses to experimentally induced psychosocial stress. In the current study, we used functional magnetic resonance imaging (fMRI) to compare regional brain activations across 5-HTTLPR genotypes in subjects performing the Montreal Imaging Stress Task (MIST). Subjects with an SS genotype had significant greater increases in cortisol concentrations after the task than subjects with at least one long 5-HTTLPR allele. Additionally, relative to L carriers, the SS group had greater activation in the dorsomedial prefrontal cortex(dmPFC), dorsal anterior cingulate cortex, anterior insula.

Genotype, resilience and function and physical activity post hip fracture

BACKGROUND

Individuals who are resilient are more likely to engage in functional tasks and exercise post hip fracture. There may be a genetic predisposition to being resilient.

OBJECTIVES

This study tested the direct and indirect association of 10 candidate genes, age, cognition, gender, comorbidities, pain and social activity on resilience, function and exercise post hip fracture.

METHOD

This was a descriptive study including 172 community dwelling older adults. Measures included: age, gender, cognition (Modified Mini Mental Status Exam), comorbidities, social activities (self-report), DNA (GRM1, NTRK1, NTRK2, GNB3, NPY, SLC6A15. SLC6A4, BDNF, CR1TR1, FKBP5), pain (areas of pain and Numeric Rating Scale), function (Physical and Instrumental Activities of Daily Living; Lower Extremity Gains Score; Short Physical Performance Battery; Grip Strength) and exercise (Yale Physical Activity Scale).

RESULTS

The majority of participants were Caucasian (93%), 50% were women and the average age was 81.09 (SD = 7.42). There were significant associations between resilience and single nucleotide polymorphisms from GRM1, NTRK1, NTRK2, GNB3, NPY and SLC6A15. Resilience, age, cognition, social activity, pain and genetic variability were directly and/or indirectly associated with exercise and/or function.

DISCUSSION

This study highlights the importance of resilience for engagement in exercise and function after hip fracture and provides preliminary evidence for a genetic role for resilience.

A Systematic Review of Genetic Influence on Psychological Resilience

When exposed to adversity, some individuals are at an increased risk of posttraumatic stress disorder, experiencing persistent biopsychosocial disturbances, whereas others adapt well, described as resilience. Resilience is a complex biopsychosocial phenomenon conceptualized as adaptation to adversity influenced by an individual’s genetic variants, epistasis, epigenetics, and gene-by-environment interactions. Studies on psychological resilience have focused on behavioral and psychosocial variables with far less examination of the genetic contributions. The purpose of this review is to identify specific genetic variants contributing to the biological capacity for psychological resilience. PubMed and PsycINFO were searched using the following key words: psychological resilience AND genotype(s). Additional articles were identified from the Human Genome Epidemiology Navigator using the term resilience, psychological. Ten studies met the criteria. Six genes were empirically associated with psychological resilience: serotonin-transporter-linked polymorphic region ( 5-HTTLPR), dopamine receptor D4, brain-derived neurotrophic factor ( BDNF), corticotropin-releasing hormone receptor 1, oxytocin receptor and regulator of G-protein signaling 2 . The findings of this systematic review suggest that the L/L or L’/L’ genotype of 5-HTTLPR and rs25531 in children/adolescents and the S/S or S’/S’ genotype in adults are most frequently related to resilience. Additionally, the Val/Val genotype of rs6265 in BDNF in Caucasians was also associated with resilience. There are numerous factors contributing to the complexity of determining the genetic influence on resilience including analysis of rs25531, assumptions of the mode of inheritance, operationalization of resilience, demographic and population characteristics, sample size, and other types of genetic influence including epistasis and epigenetics. While current evidence is supportive, further investigation of the genetic influence on resilience is required.

The interplay of genetic and environmental factors in shaping well-being across the lifespan: Evidence from the serotonin transporter gene

BACKGROUND

Converging evidence suggests that well-being plays an important role in promoting and maintaining mental health across the life span. It has been shown that well-being has a considerable heritable component, but little is known about the specific genes involved.

METHODS

In this study, we investigated a healthy sample (N = 298) that was genotyped for the serotonin transporter-linked polymorphic region (5-HTTLPR). We hypothesized that 5-HTTLPR gene variation would influence well-being, and additionally investigated interaction effects with age and the environmental influence of early life stress (ELS).

RESULTS

Using multiple regression, our results showed a significant three-way interaction between genotype, ELS, and age. Exploration of this interaction showed that young subjects had decreased levels of well-being if they were exposed to ELS and homozygous for the short variant of 5-HTTLPR. This relationship was reversed in old age: subjects that were exposed to ELS and carried the long variant of 5-HTTLPR had decreased levels of well-being.

CONCLUSION

Our results indicate that genetic and environmental factors have joint effects on well-being that are susceptible to profound changes across the life span.

Neurobiological Mechanisms of Stress Resilience and Implications for the Aged Population

BACKGROUND

Stress is a common reaction to an environmental adversity, but a dysregulation of the stress response can lead to psychiatric illnesses such as major depressive disorder (MDD), post-traumatic stress disorder (PTSD), and anxiety disorders. Yet, not all individuals exposed to stress will develop psychiatric disorders; those with enhanced stress resilience mechanisms have the ability to adapt successfully to stress without developing persistent psychopathology. Notably, the potential to enhance stress resilience in at-risk populations may prevent the onset of stress-induced psychiatric disorders. This novel idea has prompted a number of studies probing the mechanisms of stress resilience and how it can be manipulated.

METHODS

Here, we review the neurobiological factors underlying stress resilience, with particular focus on the serotoninergic (5-HT), glutamatergic, and γ-Aminobutyric acid (GABA) systems, as well as the hypothalamic-pituitary axis (HPA) in rodents and in humans. Finally, we discuss stress resiliency in the context of aging, as the likelihood of mood disorders increases in older adults.

RESULTS

Interestingly, increased resiliency has been shown to slow aging and improved overall health and quality of life. Research in the neurobiology of stress resilience, particularly throughout the aging process, is a nascent, yet, burgeoning field.

CONCLUSION

Overall, we consider the possible methods that may be used to induce resilient phenotypes, prophylactically in at-risk populations, such as in military personnel or in older MDD patients. Research in the mechanisms of stress resilience may not only elucidate novel targets for antidepressant treatments, but also provide novel insight about how to prevent these debilitating disorders from developing.

Resilience in aging: literature review

Psychological resilience is comprised of an adaptive functioning standard before the current and accumulated risks of life. Furthermore, it has a comprehensive range of psychological resources which are essential to overcome adversities, such as personal competences, self-beliefs and interpersonal control which interact with the social networks support. The objectives are to show the concepts of psychological resilience in elderly, relative to dominant theoretical models and the main data about psychological resilience in aging, found in an international and Brazilian review from 2007 to 2013. The descriptors "resilience, psychological resilience and aging", "resiliência e envelhecimento, velhice e velho", were used in PubMed, PsychInfo, SciELO and Pepsic databases. Fifty three international and eleven national articles were selected. The international articles were classified in four categories: psychological and social coping resources, emotional regulation before stressing experiences, successful resilience and aging and correlates, and resilience measures. The Brazilian articles were grouped in three: psychological and social resources, resilience in carers and theory review. Articles on psychological resources and on emotional regulation prevailed as key factors associated with psychological resilience in aging.

The Impact of Genetics on Physical Resilience and Successful Aging

Objective: To better understand the impact of genetics on resilience and successful aging, we tested a model of successful aging. Method: This was a descriptive study with a single interview and blood draw done with residents in a continuing care retirement community. Five genes associated with resilience were included in the model. The hypothesis was tested using structural equation modeling. Results: A total of 116 participants completed the survey. Two SNPs from SLC6A4 (rs25533 and rs1042173) and age were the only variables associated with physical resilience and explained 9% of the variance. Cognitive status, age, and depression were directly associated with successful aging; variance in rs25532 or rs1042173, resilience, and pain were indirectly associated with successful aging through depression. Discussion: Continued research to replicate these findings is needed so as to be able to recognize older adults at risk of low physical resilience and implement appropriate interventions.

Candidate SNP associations of optimism and resilience in older adults: exploratory study of 935 community-dwelling adults

OBJECTIVE

Optimism and resilience promote health and well-being in older adults, and previous reports suggest that these traits are heritable. We examined the association of selected single-nucleotide polymorphisms (SNPs) with optimism and resilience in older adults.

DESIGN

Candidate gene association study that was a follow-on at the University of California, San Diego, sites of two NIH-funded multi-site longitudinal investigations: Women's Health Initiative (WHI) and SELenium and vitamin E Cancer prevention Trial (SELECT).

PARTICIPANTS

426 women from WHI older than age 50 years, and 509 men older than age 55 years (age 50 years for African American men) from SELECT.

MEASUREMENTS

65 candidate gene SNPs that were judged by consensus, based on a literature review, as being related to predisposition to optimism and resilience, and 31 ancestry informative marker SNPs, genotyped from blood-based DNA samples and self-report scales for trait optimism, resilience, and depressive symptoms.

RESULTS

Using a Bonferroni threshold for significant association (p = 0.00089), there were no significant associations for individual SNPs with optimism or resilience in single-locus analyses. Exploratory multi-locus polygenic analyses with p <0.05 showed an association of optimism with SNPs in MAOA, IL10, and FGG genes, and an association of resilience with a SNP in MAOA gene.

CONCLUSIONS

Correcting for Type I errors, there were no significant associations of optimism and resilience with specific gene SNPs in single-locus analyses. Positive psychological traits are likely to be genetically complex, with many loci having small effects contributing to phenotypic variation. Our exploratory multi-locus polygenic analyses suggest that larger sample sizes and complementary approaches involving methods such as sequence-based association studies, copy number variation analyses, and pathway-based analyses could be useful for better understanding the genetic basis of these positive psychological traits.

Connectivity underlying emotion conflict regulation in older adults with 5-HTTLPR short allele: a preliminary investigation

OBJECTIVE

The serotonin transporter polymorphism short (s) allele is associated with heightened emotional reactivity and reduced emotion regulation, which increases vulnerability to depression and anxiety disorders. We investigated behavioral and neural markers of emotion regulation in community-dwelling older adults, contrasting s allele carriers and long allele homozygotes.

METHODS

Participants (N = 26) completed a face-word emotion conflict task during functional magnetic resonance imaging, in which facilitated regulation of emotion conflict was observed on face-word incongruent trials following another incongruent trial (i.e., emotional conflict adaptation).

RESULTS

There were no differences between genetic groups in behavioral task performance or neural activation in postincongruent versus postcongruent trials. By contrast, connectivity between dorsal anterior cingulate cortex (ACC) and pregenual ACC, regions previously implicated in emotion conflict regulation, was impaired in s carriers for emotional conflict adaptation.

CONCLUSION

This is the first demonstration of an association between serotonin transporter polymorphism and functional connectivity in older adults. Poor dorsal ACC-pregenual ACC connectivity in s carriers may be one route by which these individuals experience greater difficulty in implementing effective emotional regulation, which may contribute to their vulnerability for affective disorders.

Investigation of association of serotonin transporter and monoamine oxidase-A genes with Alzheimer's disease and depression in the VITA study cohort: a 90-month longitudinal study

Alzheimer's disease (AD) and depression (DE) are common psychiatric disorders strongly intertwined with one another. Nevertheless, etiology and early diagnosis of the disorders are still elusive. Several genetic variations have been suggested to associate with AD and DE, particularly in genes involved in the serotonergic system such as the serotonin transporter (SERT/SLC6A4), responsible for the removal from the synaptic cleft, and the monoamine-oxidase-A (MAOA), responsible for the presynaptic degradation of serotonin. Here, we attempt to characterize this pleiotropic effect for the triallelic SERT gene-linked polymorphic region (5HTTLPR) and for the MAOA-uVNTR, in participants in the Vienna-Transdanube-Aging (VITA)-study. The VITA-study is a community-based longitudinal study following a birth cohort (75 years old at baseline examination, n = 606) from Vienna for a period of 90 months with a regular follow-up interval of 30 months. Our main finding, confirming previous reports, is that the 5HTTLPR S-allele is a risk allele for DE (OR = 1.55 CI 95% 1.03-2.32) and its carriers had a steeper increase in SGDS sum score. No association to AD was found. MAOA-uVNTR did not associate with either AD or DE. However, in AD MAOA-uVNTR S-allele carriers a steeper increase of HAMD and STAI1 sum scores (P < 0.05) was observed. Although the VITA-study cohort is rather small with low power to detect gene alterations, the uniqueness of this very thoroughly investigated and homogenous cohort strengthens the results through exceptional data collection. Still, reinvestigation in a larger cohort similar to this, as well as a meta-analysis, is important to confirm these results.

Perceived stress is associated with subclinical cerebrovascular disease in older adults

OBJECTIVE

To examine the association of perceived stress with magnetic resonance imaging (MRI) markers of subclinical cerebrovascular disease in an elderly cohort.

METHODS

Using a cross-sectional study of a community-based cohort in Chicago, 571 adults (57% women; 58.1% African American; 41.9% non-Hispanic white; mean [SD] age: 79.8 [5.9] years) from the Chicago Health and Aging Project, an epidemiologic study of aging, completed questionnaires on perceived stress, medical history, and demographics as part of an in-home assessment and 5 years later underwent a clinical neurologic examination and MRI of the brain. Outcome measures were volumetric MRI assessments of white matter hyperintensity volume (WMHV), total brain volume (TBV), and cerebral infarction.

RESULTS

Stress was measured with six items from the Perceived Stress Scale (PSS); item responses, ranging from never (0) to often (3), were summed to create an overall stress score (mean [SD]: 4.9 [3.3]; range: 0-18). Most participants had some evidence of vascular disease on MRI, with 153 participants (26.8%) having infarctions. In separate linear and logistic regression models adjusted for age, sex, education, race, and time between stress assessment and MRI, each one-point increase in PSS score was associated with significantly lower TBV (coefficient = -0.111, SE = 0.049, t[563] = -2.28, p = 0.023) and 7% greater odds of infarction (odds ratio: 1.07; 95% confidence interval: 1.01, 1.13; Wald χ(2)[1] = 4.90; p = 0.027). PSS scores were unrelated to WMHV. Results were unchanged with further adjustment for smoking, body mass index, physical activity, history of heart disease, stroke, diabetes, hypertension, depressive symptoms, and dementia.

CONCLUSIONS

Greater perceived stress was significantly and independently associated with cerebral infarction and lower brain volume assessed 5 years later in this elderly cohort.

Role of 5-HTTLPR polymorphism in the development of the inward/outward personality organization: a genetic association study

Reciprocity with primary caregivers affects subjects' adaptive abilities toward the construction of the most useful personal meaning organization (PMO) with respect to their developmental environment. Within cognitive theory the post-rationalist approach has outlined two basic categories of identity construction and of regulation of cognitive and emotional processes: the Outward and the Inward PMO. The presence of different, consistent clinical patterns in Inward and Outward subjects is paralleled by differences in cerebral activation during emotional tasks on fMRI and by different expression of some polymorphisms in serotonin pathways. Since several lines of evidence support a role for the 5-HTTLPR polymorphism in mediating individual susceptibility to environmental emotional stimuli, this study was conducted to investigate its influence in the development of the Inward/Outward PMO.

PMO was assessed and the 5-HTTLPR polymorphism investigated in 124 healthy subjects who were subdivided into an Inward (n = 52) and an Outward (n = 72) group.

Case-control comparisons of short allele (S) frequencies showed significant differences between Inwards and Outwards (p = 0.036, χ2 test; p = 0.026, exact test). Genotype frequencies were not significantly different although values slightly exceeded p≤0.05 (p = 0.056, χ2 test; p = 0.059, exact test). Analysis of the 5-HTTLPR genotypes according to the recessive inheritance model showed that the S/S genotype increased the likelihood of developing an Outward PMO (p = 0.0178, χ2 test; p = 0.0143, exact test; OR = 3.43, CI (95%) = 1.188–9.925). A logistic regression analysis confirmed the association between short allele and S/S genotypes with the Outward PMO also when gender and age were considered. However none of the differences remained significant after correction for multiple testing, even though using the recessive model they approach significance.

Overall our data seem to suggest a putative genetic basis for interindividual differences in PMO development.

Association between Neurocognitive Impairment and the Short Allele of the 5-HTT Promoter Polymorphism in Depression: A Pilot Study

Depression has been shown to be associated with cognitive deficits in various cognitive domains. However, it is still unclear which factors contribute to cognitive impairment. The objective of this study was to find out whether a functional polymorphism in the promoter region of the serotonin transporter (5-HTTLPR) gene is associated with the impairment of cognitive functioning among depressed patients. In a pilot study, a sample of 19 patients with major depressive disorder (MDD) and 19 healthy controls was investigated with an extensive psychiatric and neuropsychological examination. All participants were genotyped for 5-HTTLPR. Depressed patients with the short allele of the 5-HTT promoter region exhibited inferior cognitive performance compared to patients with the long allele polymorphism. In healthy controls, no association between genotype and cognitive performance was found. The result suggests that in MDD patients with the short allele of the 5-HTTLPR polymorphism the vulnerability to cognitive impairment is increased compared to MDD patients without the short allele inheritance. These preliminary findings need to be confirmed in a larger cohort of MDD patients.

Serotonin transporter genotype and mild traumatic brain injury independently influence resilience and perception of limitations in veterans

Evidence indicates that individuals with the 5-HTTLPR variant short/short genotype have increased sensitivity to both positive and negative perceptions of perceived social support. The aim of this study was to evaluate this association among Veterans in the context of mild traumatic brain injury (TBI). As part of a larger TBI center, we performed a cross-sectional study of 67 OEF/OIF/OND Veterans (41 with TBI and 26 controls without TBI) who completed the questionnaires and consented to genetic testing. The primary measures included the Connor-Davidson Resilience Scale (CDRISC) and the Perceived Limitations in community participation subscale of the Community Reintegration of Service Members Instrument (CRIS-PL). Both 5-HTTLPR genotype and TBI status were independently associated with the CRIS-PL (p = .009 for genotype, p = .001 for TBI) and the CDRISC (p = .015 for genotype, p = .003 for TBI) scores. This study suggests that both the 5-HTTLPR genotype and TBI status independently, in an almost equal but opposite direction, influence resilience and perceived limitations to social participation. Further, resilience appears more sensitive to perceived limitations in Veterans carrying an S'S' genotype than in L' carriers, but only in the context of having sustained a TBI. While having a TBI appeared to increase a Veteran's sensitivity to social stress, the Veteran's who were L' allele carriers with a TBI fared the worst, with lower resilience and more perceived limitations for community participation compared to L' carrier Veterans without a TBI or Veterans with the S'S' genotype regardless of TBI status.

Variability Over Time-Since- Diagnosis in the Protective Effect of Psychological Resilience Against Depression in Australian Prostate Cancer Patients

Although there is some evidence that psychological resilience may “buffer” against depression following major stressors, no data have been reported on the nature and variability of this buffering effect among prostate cancer patients during the 5 years following their initial diagnosis. Patients from two sites in Australia and who had received their initial diagnosis within 5 years ( n = 255) were surveyed, and the results indicated that there was a significant inverse relationship between resilience and depression in the overall data, but that was mostly accounted for by a single factor of the resilience scale (“Confidence to cope with change”). Variability in that buffering effect was noted over time since diagnosis, with peaks during the first 6 months, at 24 and 60 months. These findings support the argument to develop focused psychiatric interventions at various periods following a diagnosis of prostate cancer.