Personality traits relate to chronotype at both the phenotypic and genetic level.

INTRODUCTION: Diurnal preferences have been linked to personality but often with mixed results. The present study examines the relationships between sleep timing (chronotype), diurnal preferences, and the Five-Factor Model of personality traits at the phenotypic and genetic level. METHODS: Self- and informant-reports of the NEO Personality Inventory-3, self-reports of the Munich Chronotype Questionnaire, and DNA samples were available for 2,515 Estonian adults (Mage  = 45.76 years; 59% females). Genetic correlations were obtained through summary statistics of genome-wide association studies. RESULTS: Results showed that higher Conscientiousness and lower Openness to Experience were significant predictors of earlier chronotype. At the level of facets, we found that more straightforward (A2) and excitement-seeking (E5), yet less self-disciplined (C5) people were more likely to have later chronotypes. The nuance-level Polypersonality score was correlated with chronotype at r = .28 (p < .001). Conscientiousness and Openness were genetically related with diurnal preferences. The polygenic score for morningness-eveningness significantly predicted the Polypersonality score. CONCLUSION: Phenotypic measures of chronotype and personality showed significant associations at all three of levels of the personality hierarchy. Our findings indicate that the relationship between personality and morningness-eveningness is partly due to genetic factors. Future studies are necessary to further refine the relationship.

The relationship between the Five-Factor Model personality traits and peptic ulcer disease in a large population-based adult sample.

The current study examined the relationship between the Five-Factor Model personality traits and physician-confirmed peptic ulcer disease (PUD) diagnosis in a large population-based adult sample, controlling for the relevant behavioral and sociodemographic factors. Personality traits were assessed by participants themselves and by knowledgeable informants using the NEO Personality Inventory-3 (NEO PI-3). When controlling for age, sex, education, and cigarette smoking, only one of the five NEO PI-3 domain scales - higher Neuroticism - and two facet scales - lower A1: Trust and higher C1: Competence - made a small, yet significant contribution (p < 0.01) to predicting PUD in logistic regression analyses. In the light of these relatively modest associations, our findings imply that it is certain behavior (such as smoking) and sociodemographic variables (such as age, gender, and education) rather than personality traits that are associated with the diagnosis of PUD at a particular point in time. Further prospective studies with a longitudinal design and multiple assessments would be needed to fully understand if the FFM personality traits serve as risk factors for the development of PUD.

Effect of birth weight, maternal education and prenatal smoking on offspring intelligence at school age.

To examine the combined effect of birth weight, mothers' education and prenatal smoking on psychometrically measured intelligence at school age 1,822 children born in 1992-1999 and attending the first six grades from 45 schools representing all of the fifteen Estonian counties with information on birth weight, gestational age and mother's age, marital status, education, parity and smoking in pregnancy, and intelligence tests were studied. The scores of Raven's Standard Progressive Matrices were related to the birth weight: in the normal range of birth weight (>or=2500 g) every 500 g increase in birth weight was accompanied by around 0.7-point increase in IQ scores. A strong association between birth weight and IQ remained even if gestational age and mother's age, marital status, education, place of residence, parity and smoking during pregnancy have been taken into account. Maternal prenatal smoking was accompanied by a 3.3-point deficit in children's intellectual abilities. Marriage and mother's education had an independent positive correlation with offspring intelligence. We concluded that the statistical effect of birth weight, maternal education and smoking in pregnancy on offspring's IQ scores was remarkable and remained even if other factors have been taken into account.

Association of traffic behavior with personality and platelet monoamine oxidase activity in schoolchildren.

PURPOSE: Estimations, attitudes and behavioral decisions in everyday life, including traffic-related situations, are influenced by personality traits. It is known that that there is a strong link between certain personality traits, particularly impulsivity, and central serotonergic functioning. This study examined associations between traffic behavior, personality and platelet monoamine oxidase activity, a marker of central nervous system serotonergic neurotransmission, in schoolchildren. METHODS: Participants were 483 schoolchildren (aged 15.3 +/- .5 years) who filled in questionnaires on traffic behavior and personality. Platelet monoamine oxidase activity was measured radioenzymatically. RESULTS: Simple logistic regression analysis revealed that subjects with riskier traffic behavior had higher impulsivity (both adaptive as maladaptive facets) as well as lower Openness, Agreeableness, and Conscientiousness. In multiple logistic regression analysis, many of these associations became nonsignificant, but the high traffic risk group was more likely to have lower Agreeableness and lower platelet MAO activity. Low platelet MAO activity was a significant predictor of risky traffic behavior only in girls who were also influenced by higher Excitement Seeking. Smoking was an independent predictor of all groups with high traffic risks. CONCLUSION: Risky traffic behavior in schoolchildren is associated with basic personality dimensions, most consistently with Agreeableness, and with different aspects of impulsivity. Some of these traits, particularly in girls, may be related to central serotonergic neuronal activity.

Association between substance use, personality traits, and platelet MAO activity in preadolescents and adolescents.

This study examined the relationship between alcohol/illicit drug use, the Five-Factor Model (FFM) personality traits, aggressiveness (Agg), and hyperactivity (Hyp), and platelet monoamine oxidase (MAO) activity in a population-derived representative sample of preadolescents and adolescents (n=1172). Alcohol and illicit drug use was self-reported. The FFM personality inventories were filled in by mothers of the participants, and Agg and Hyp were rated by their class teachers. Higher scores in extraversion (E), Agg, and Hyp and lower scores in conscientiousness (C) together with older age were significant predictors of more frequent alcohol use in adolescents. No significant association was found between alcohol illicit drug use, and platelet MAO activity.