Genetic structure of personality factors and bipolar disorder in families segregating bipolar disorder

Personality Traits Interact With Sleep and Biological Rhythm in Patients With Bipolar Disorder

ABSTRACT

Sleep disturbances and circadian rhythm changes in bipolar disorder (BD) may have behavioral components as well as biological components. This study aimed to examine the relationship between personality traits, sleep and circadian rhythm in BD. A total of 150 participants with BD, and 150 healthy controls completed the Big Five Personality Test-50 (B5PT-50-TR), Biological Rhythm Interview of Assessment in Neuropsychiatry (BRIAN), Functioning Assessment Short Test (FAST), Pittsburgh Sleep Quality Index (PSQI), Young Mania Rating Scale and Beck Depression Inventory. In the BD group, B5PT-50-TR emotional stability and openness subscale scores were significantly lower in comparison with the healthy control group. Agreeableness and emotional stability subscales were covariates for the BRIAN sleep subscale and emotional stability was a covariate for PSQI total score. Emotional instability might be a vulnerability factor for sleep disorders and biological rhythm abnormalities in BD. Improvement in emotional instability may relieve sleep disorders and biological rhythm, thereby leading to better treatment outcomes in BD.

Creativity and Bipolar Disorder: A Shared Genetic Vulnerability

Bipolar disorder is a lifelong mood disorder characterized by extreme mood swings between mania and depression. Despite fitness costs associated with increased mortality and significant impairment, bipolar disorder has persisted in the population with a high heritability and a stable prevalence. Creativity and other positive traits have repeatedly been associated with the bipolar spectrum, particularly among unaffected first-degree relatives and those with milder expressions of bipolar traits. This suggests a model in which large doses of risk variants cause illness, but mild to moderate doses confer advantages, which serve to maintain bipolar disorder in the population. Bipolar disorder may thus be better conceptualized as a dimensional trait existing at the extreme of normal population variation in positive temperament, personality, and cognitive traits, aspects of which may reflect a shared vulnerability with creativity. Investigations of this shared vulnerability may provide insight into the genetic mechanisms underlying illness and suggest novel treatments.

Transmissibility and familiality of NEO personality dimensions in a sample of Korean families with schizophrenia

Categorical syndromes such as schizophrenia may represent complexes of many continuous psychological structural phenotypes along several dimensions of personality development/degeneration. The present study investigated the heritability and familiality of Neuroticism-Extraversion-Openness to experience (NEO) personality dimensions in Korean families with schizophrenic linkage disequilibrium (LD).We have recruited 204 probands (with schizophrenia) with their parents and siblings whenever possible. We have used NEO questionnaires for measuring personality and symptomatic dimensions. Heritabilities of personality dimensions in total 543 family members were estimated using Sequential Oligogenic Linkage Analysis Routines (SOLAR). Personality dimensions in total family members were compared with those in 307 healthy unrelated controls for measuring the familialities using ANOVA analysis.Four of the 5 NEO variables were significantly heritable and were included in the subsequent analyses. The 3 groups (control, unaffected first-degree relative, case) were found to be significantly different and with the expected order of average group scores for all heritable dimensions.Our results show that the aberrations in several personality dimensions could form the complexity of schizophrenic syndrome as a result of genetic-environment coactions or interactions in spite of some limitations (recruited family, phenotyping).

A genome-wide quantitative trait locus (QTL) linkage scan of NEO personality factors in Latino families segregating bipolar disorder

Personality traits have been suggested as potential endophenotypes for Bipolar Disorder (BP), as they can be quantitatively measured and show correlations with BP. The present study utilized data from 2,745 individuals from 686 extended pedigrees originally ascertained for having multiplex cases of BP (963 cases of BPI or schizoaffective BP). Subjects were assessed with the NEO Personality Inventory, Revised (NEO PI-R) and genotyped using the Illumina HumanLinkage-24 Bead Chip, with an average genetic coverage of 0.67 cM. Two point linkage scores were calculated for each trait as a quantitative variable using SOLAR (Sequential Oligogenic Linkage Analysis Routines). Suggestive evidence for linkage was found for neuroticism at 1q32.1 (LOD = 2.52), 6q23.3 (2.32), 16p12 (2.79), extraversion at 4p15.3 (2.33), agreeableness at 4q31.1 (2.37), 5q34 (2.80), 7q31.1 (2.56), 16q22 (2.52), and conscientiousness at 4q31.1 (2.50). Each of the above traits have been shown to be correlated with the broad BP phenotype in this same sample. In addition, for the trait of openness, we found significant evidence of linkage to chromosome 3p24.3 (rs336610, LOD = 4.75) and suggestive evidence at 1q43 (2.74), 5q35.1 (3.03), 11q14.3 (2.61), 11q21 (2.30), and 19q13.1 (2.52). These findings support previous linkage findings of the openness trait to chromosome 19q13 and the agreeableness trait to 4q31 and identify a number of new loci for personality endophenotypes related to bipolar disorder.

Positive Traits in the Bipolar Spectrum: The Space between Madness and Genius

Bipolar disorder is a severe, lifelong mood disorder for which little is currently understood of the genetic mechanisms underlying risk. By examining related dimensional phenotypes, we may further our understanding of the disorder. Creativity has a historical connection with the bipolar spectrum and is particularly enhanced among unaffected first-degree relatives and those with bipolar spectrum traits. This suggests that some aspects of the bipolar spectrum may confer advantages, while more severe expressions of symptoms negatively influence creative accomplishment. Creativity is a complex, multidimensional construct with both cognitive and affective components, many of which appear to reflect a shared genetic vulnerability with bipolar disorder. It is suggested that a subset of bipolar risk variants confer advantages as positive traits according to an inverted-U-shaped curve with clinically unaffected allele carriers benefitting from the positive traits and serving to maintain the risk alleles in the population. The association of risk genes with creativity in healthy individuals (e.g., NRG1), as well as an overall sharing of common genetic variation between bipolar patients and creative individuals, provides support for this model. Current findings are summarized from a multidisciplinary perspective to demonstrate the feasibility of research in this area to reveal the mechanisms underlying illness.

Personality Polygenes, Positive Affect, and Life Satisfaction

Approximately half of the variation in wellbeing measures overlaps with variation in personality traits. Studies of non-human primate pedigrees and human twins suggest that this is due to common genetic influences. We tested whether personality polygenic scores for the NEO Five-Factor Inventory (NEO-FFI) domains and for item response theory (IRT) derived extraversion and neuroticism scores predict variance in wellbeing measures. Polygenic scores were based on published genome-wide association (GWA) results in over 17,000 individuals for the NEO-FFI and in over 63,000 for the IRT extraversion and neuroticism traits. The NEO-FFI polygenic scores were used to predict life satisfaction in 7 cohorts, positive affect in 12 cohorts, and general wellbeing in 1 cohort (maximal N = 46,508). Meta-analysis of these results showed no significant association between NEO-FFI personality polygenic scores and the wellbeing measures. IRT extraversion and neuroticism polygenic scores were used to predict life satisfaction and positive affect in almost 37,000 individuals from UK Biobank. Significant positive associations (effect sizes <0.05%) were observed between the extraversion polygenic score and wellbeing measures, and a negative association was observed between the polygenic neuroticism score and life satisfaction. Furthermore, using GWA data, genetic correlations of −0.49 and −0.55 were estimated between neuroticism with life satisfaction and positive affect, respectively. The moderate genetic correlation between neuroticism and wellbeing is in line with twin research showing that genetic influences on wellbeing are also shared with other independent personality domains.

BDNF Val66Met genotype and neuroticism predict life stress: A longitudinal study from childhood to adulthood

The brain-derived neurotrophic factor gene (BDNF) Val66Met polymorphism and life stress have been associated with negative emotionality (e.g., neuroticism), but relevant evidence is far from unequivocal. Possible confounding factors include the type and timing of stressful events measured, such as childhood adversity vs. recent stressful events, and variable gene × environment interactions. The aim of this study was to longitudinally assess the BDNF Val66Met polymorphism and environment interaction effect on neuroticism in a population representative sample, depending upon the type of stress, gender and family relations. In the original older cohort of the Estonian Children Personality Behavior and Health Study (ECPBHS, n=593), neuroticism was measured at age 15 (parental assessment), 18 and 25 (self-assessments). Childhood stress was reported at age 15, quality of family relations was measured at age 18, and recent stressful life events at age 25. The BDNF Val66Met polymorphism interacted with recent stressful life events, but not with childhood adversities, to impact neuroticism. Interestingly, in female participants, neuroticism at age 18 predicted future stressful life events dependent upon genotype: individuals with Val/Val genotype and high neuroticism experienced higher, but Met-allele carriers with high neuroticism lower stress exposure at age 25. Similar tendencies were observed using parental assessments at age 15. The protective effect of Met-allele in the high stress exposure group could result from better early family environment. In conclusion, we herewith provide further evidence for a role of BDNF gene variance contributing to plasticity in response to environmental demands.

Temperament as a risk factor for obesity and affective disorders in obese patients in a Polish sample

AIMS

The main purpose of the study was to investigate temperament traits postulated in the Regulative Theory of Temperament that may contribute as risk factors to obesity and, potentially, to affective disorders in obese patients.

METHOD

A cross-sectional design was applied in this study. The study was conducted on a group of 163 obese patients (BMI > 35) that included 59 men and 104 women compared with a control group that included 89 men and 113 women who were non-obese. Temperament was assessed using the formal characteristics of behaviour-temperament inventory (FCB-TI).

RESULTS

Obese patients compared with a control group scored lower in briskness, endurance and activity, and higher in perseveration. When compared with obese men, obese women had higher levels of perseveration and emotional reactivity, and showed lower levels of activity.

CONCLUSIONS

Temperament traits, including low levels of briskness, endurance and activity, may serve as risk factors for the development of obesity. Low levels of these traits with accompanying high levels of perseveration may potentially contribute as risk factors for affective disorders in obese patients. The findings suggest that obese women are at somewhat greater risk than obese men for the development of affective disorders.

Pathway analysis of genome-wide association datasets of personality traits

Although several genome-wide association (GWA) studies of human personality have been recently published, genetic variants that are highly associated with certain personality traits remain unknown, due to difficulty reproducing results. To further investigate these genetic variants, we assessed biological pathways using GWA datasets. Pathway analysis using GWA data was performed on 1089 Korean women whose personality traits were measured with the Revised NEO Personality Inventory for the 5-factor model of personality. A total of 1042 pathways containing 8297 genes were included in our study. Of these, 14 pathways were highly enriched with association signals that were validated in 1490 independent samples. These pathways include association of: Neuroticism with axon guidance [L1 cell adhesion molecule (L1CAM) interactions]; Extraversion with neuronal system and voltage-gated potassium channels; Agreeableness with L1CAM interaction, neurotransmitter receptor binding and downstream transmission in postsynaptic cells; and Conscientiousness with the interferon-gamma and platelet-derived growth factor receptor beta polypeptide pathways. Several genes that contribute to top-ranked pathways in this study were previously identified in GWA studies or by pathway analysis in schizophrenia or other neuropsychiatric disorders. Here we report the first pathway analysis of all five personality traits. Importantly, our analysis identified novel pathways that contribute to understanding the etiology of personality traits.