Serotonin 2A receptor gene polymorphism and personality traits: no evidence for significant association

Emotional dysregulation, alexithymia and neuroticism: a systematic review on the genetic basis of a subset of psychological traits

Neuroticism, alexithymia and emotion dysregulation are key traits and known risk factors for several psychiatric conditions. In this systematic review, the aim is to evaluate the genetic contribution to these psychological phenotypes. A systematic review of articles found in PubMed was conducted. Search terms included 'genetic', 'GWAS', 'neuroticism', 'alexithymia' and 'emotion dysregulation'. Risk of bias was assessed utilizing the STREGA checklist. Two hundred two papers were selected from existing literature based on the inclusion and exclusion criteria. Among these, 27 were genome-wide studies and 175 were genetic association studies. Single gene association studies focused on selected groups of genes, mostly involved in neurotransmission, with conflicting results. GWAS studies on neuroticism, on the other hand, found several relevant and replicated intergenic and intronic loci affecting the expression and regulation of crucial and well-known genes (such as DRD2 and CRHR1). Mutations in genes coding for trascriptional factors were also found to be associated with neuroticism (DCC, XKR6, TCF4, RBFOX1), as well as a noncoding regulatory RNA (LINC00461). On the other hand, little GWAS data are available on alexythima and emotional dysregulation.

The case for conscientiousness: evidence and implications for a personality trait marker of health and longevity

PURPOSE

Recent initiatives by major funding agencies have emphasized translational and personalized approaches (e.g., genetic testing) to health research and health management. While such directives are appropriate, and will likely produce tangible health benefits, we seek to highlight a confluence of several lines of research showing relations between the personality dimension of conscientiousness and a variety of health-related outcomes.

METHODS

Using a modified health process model, we review the compelling evidence linking conscientiousness to health and disease processes, including longevity, diseases, morbidity-related risk factors, health-related psychophysiological mechanisms, health-related behaviors, and social environmental factors related to health.

CONCLUSION

We argue the accumulated evidence supports greater integration of conscientiousness into public health, epidemiological, and medical research, with the ultimate aim of understanding how facilitating more optimal trait standing might foster better health.

A genome-wide scan for Eysenckian personality dimensions in adolescent twin sibships: psychoticism, extraversion, neuroticism, and lie

We report the first genome-wide scan of adolescent personality. We conducted a genome-wide scan to detect linkage for measures of adolescent Psychoticism, Extraversion, Neuroticism, and Lie from the Junior Eysenck Personality Questionnaire. Data are based on 1,280 genotyped Australian adolescent twins and their siblings. The highest linkage peaks were found on chromosomes 16 and 19 for Neuroticism, on chromosomes 1, 7, 10, 13 m, and 18 for Psychoticism, and on chromosomes 2 and 3 for Extraversion.

Frontolimbic serotonin 2A receptor binding in healthy subjects is associated with personality risk factors for affective disorder

BACKGROUND

Serotonergic dysfunction has been associated with affective disorders. High trait neuroticism, as measured on personality inventories, is a risk factor for major depression. In this study we investigated whether neuroticism is associated with serotonin 2A receptor binding in brain regions of relevance for affective disorders.

METHODS

Eighty-three healthy volunteers completed the standardized personality questionnaire NEO-PI-R (Revised NEO Personality Inventory) and underwent [(18)F]altanserin positron emission tomography imaging for assessment of serotonin 2A receptor binding. The correlation between the neuroticism score and frontolimbic serotonin 2A receptor binding was evaluated by multiple linear regression analysis with adjustment for age and gender.

RESULTS

Neuroticism correlated positively with frontolimbic serotonin 2A receptor binding [r(79) = .24, p = .028]. Post hoc analysis of the contributions from the six constituent traits of neuroticism showed that the correlation was primarily driven by two of them: vulnerability and anxiety. Indeed, vulnerability, defined as a person's difficulties in coping with stress, displayed the strongest positive correlation, which remained significant after correction for multiple comparisons (r = .35, p = .009).

CONCLUSIONS

In healthy subjects the personality dimension neuroticism and particularly its constituent trait, vulnerability, are positively associated with frontolimbic serotonin 2A binding. Our findings point to a neurobiological link between personality risk factors for affective disorder and the serotonergic transmitter system and identify the serotonin 2A receptor as a biomarker for vulnerability to affective disorder.

Polymorphism of the 5-HT(2A) receptor gene: association with stress-related indices in healthy middle-aged adults

Past research has concentrated on the stress system and personality in order to explain the variance found in cognitive performance in old age. A growing body of research is starting to focus on genetic polymorphism as an individual difference factor to explain the observed heterogeneity in cognitive function. While the functional mechanism is still under investigation, polymorphism of the 5-HT(2A) receptor gene (-1438A/G) has been linked to certain behavioral and physiological outcomes, including cortisol secretion, the expression of certain personality traits, and memory performance. It was the goal of the present study to investigate the association between the -1438A/G polymorphism and stress hormone secretion, stress-related psychological measures, and cognitive performance in a group of adults between the ages of 50 and 65. To examine these associations, 101 middle-aged adults were recruited, completed a battery of psychological questionnaires and were administered a battery of cognitive tasks that assess frontal lobe and hippocampal function. Basal and stress-reactive salivary cortisol levels were collected, at home and in the laboratory. Analyses on psychological measures showed that participants with the GG genotype reported significantly higher levels of neuroticism compared to the AG group and higher levels of depression and more emotion-based coping strategies compared to both the AG and AA group. In terms of cortisol secretion, the AA genotype was related to a significantly higher awakening cortisol response (ACR) compared to the AG and GG group and the GG genotype group displayed a greater increase in cortisol secretion following a psychosocial stressor compared to the two other groups. On measures of cognitive performance, the AA genotype group performed significantly better on a test of declarative memory and selective attention compared to the other two groups. Together, these results suggest that carriers of the GG genotype are more susceptible to low mood and display a greater potential for an overactive stress system, which may influence cognitive function in later years.

5-HT2A SNPs and the Temperament and Character Inventory

Temperamental traits, the most basic part of personality, have been largely correlated with neurotransmitter systems and are under genetic control. Among serotonin candidates, the 2A receptor (5-HT(2A)) received considerable attention. We analyzed four SNPs (rs643627, rs594242, rs6311 and rs6313) in the 5-HT(2A) gene and their association with personality traits, as measured with the Temperament and Character Inventory (TCI). The sample was composed of three sub-groups: two German sub-samples, consisting of a healthy group of 289 subjects (42.6% males, mean age: 45.2+/-14.9) and a psychiatric patient group of 111 suicide attempters (38.7% males, mean age: 39.2+/-13.6), and an Italian sub-sample, composed of 60 mood disorder patients (35.0% males, mean age: 44.0+/-14.8). Controlling for sex, age and educational level, the SNPs were not strongly associated with personality dimensions. Only the rs594242 showed an association with Self-Directedness (p=0.003) in the German sample, while rs6313 was marginally associated with Novelty Seeking (p=0.01) in the Italian sample. We conclude that 5-HT(2A) SNPs may marginally modulate personality traits but further studies are required.

Serotonin 2A receptor gene is associated with personality traits, but not to disorder, in patients with borderline personality disorder

Borderline personality disorder (BPD) is a chronic, disabling, and high-risk mental disorder characterized by a pervasive pattern of instability in regulation of emotion, interpersonal relationships, self-image, and impulse control beginning in early adulthood. BPD affects about 1%-2% of the general population and has a high mortality rate as a result of suicide and impulsive behaviour. The serotonin 2A receptor gene (HTR2A) is considered a candidate gene for BPD because multiple lines of evidence suggest that it plays an important role in suicide, impulsivity and emotional liability. To test for an association between HTR2A and BPD, we genotyped four polymorphisms, rs6313 (T102C), rs4941573, rs2296972 and rs6314 (His452Tyr), in 111 Caucasian patients with BPD and 287 Caucasian healthy controls. The program UNPHASED was used to compare allele and haplotype frequencies between cases and controls. We did not find a significant association between HTR2A and BPD based on allele, genotype or haplotype analyses. However, there were significant associations between HTR2A and personality traits in the BPD patients. The C allele of rs6313 and the A allele of rs4941573 associated with a higher Extraversion score. Our results suggest that the serotonin 2A receptor gene may not play a major role in the aetiology of borderline personality disorder, but may have a role in personality traits.

No association of 5-HT2C, 5-HT6, and tryptophan hydroxylase-1 gene polymorphisms with personality traits in the Japanese population

Serotonin 2C receptor (5-HT(2C)), serotonin 6 receptor (5-HT(6)), and tryptophan hydroxylase-1 (TPH1) genes could be candidates for personality-related genes considering the role of serotonin in various mental functions and behavior. However, a limited number of studies have investigated the association between these genes and personality traits. In the present study, we investigated the three serotonin-related genes, 5-HT(2C), 5-HT(6), and TPH1 genes, in relation to personality traits in the Japanese population. The Cys23Ser polymorphisms in the 5-HT(2C) gene, the 267T/C polymorphism of the 5-HT(6) gene, and the 779A/C polymorphisms in the TPH1 gene were genotyped in 253 healthy Japanese subjects. Personality traits were evaluated by using the Revised NEO Personality Inventory (NEO PI-R) and the State-Trait Anxiety Inventory (STAI). As a result, no significant association was observed between the polymorphisms and the NEO PI-R or the STAI scores. The present results did not provide evidence for the association between the three serotonin-related genes and personality traits. The genes might not have major role in the development of personality traits, although further investigation with larger sample size may be recommended for conclusion.

The molecular genetic architecture of human personality: beyond self-report questionnaires

Molecular genetic studies of personality began with two high impact papers in 1996 that showed provisional associations between the dopamine DRD4 exon III repeat region and Novelty Seeking/Extraversion. These first two reports were shortly followed by an investigation linking Neuroticism/Harm Avoidance with the serotonin transporter (SLC6A4) promoter region polymorphism (5-HTTLPR). In the ensuing decade, thousands of subjects have been studied for association between these genes and personality, assessed by using self-report questionnaires, with erratic success in replication of the first findings for Novelty Seeking (DRD4) and Harm Avoidance (5-HTTLPR). Small effect sizes characteristic of non-Mendelian traits, polygenic patterns of inheritance and true heterogeneity between studies confound attempts to reach a consensus regarding the role of common polymorphisms in contributing to personality domains. Nevertheless, the current state of personality genetics is far from being bleak. Several new paradigms especially functional neuroimaging or 'imaging genomics' have strengthened the connection between 5-HTTLPR and anxiety-related personality traits. The demonstrations that early environmental information can considerably strengthen and even uncover associations between genes and behavior (Caspi's seminal studies and more recently the demonstration that early environment impacts on DRD4 and Novelty Seeking) are notable and herald a new era of personality genetics. Finally, consideration of the broader phenotypic expression of common polymorphisms (e.g. the 'social brain', altruism, etc.) and the use of new experimental paradigms including neurophysiological, neuropsychological and computer games that go beyond the narrow self-report questionnaire design will enable a deeper understanding of how common genetic polymorphisms modulate human behavior. Human personality, defined by Webster as the quality or state of being a person or the complex of characteristics that distinguishes an individual, surely requires a more encompassing view towards understanding its complex molecular genetic architecture.