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There is growing evidence that personality traits are affected by many genes, all of which have very small effects. As an alternative to the largely unsuccessful search for individual polymorphisms associated with personality traits, the authors identified large sets of potentially related single nucleotide polymorphisms (SNPs) and summed them to form molecular personality scales (MPSs) with from 4 to 2,497 SNPs. Scales were derived from two thirds of a large (N = 3,972) sample of individuals from Sardinia who completed the Revised NEO Personality Inventory (P. T. Costa, Jr., & R. R. McCrae, 1992) and were assessed in a genomewide association scan. When MPSs were correlated with the phenotype in the remaining one third of the sample, very small but significant associations were found for 4 of the 5e personality factors when the longest scales were examined. These data suggest that MPSs for Neuroticism, Openness to Experience, Agreeableness, and Conscientiousness (but not Extraversion) contain genetic information that can be refined in future studies, and the procedures described here should be applicable to other quantitative traits., (PsycINFO Database Record (c) 2010 APA, all rights reserved.)

Objective: Personality traits underlie maladaptive behaviors, and cognitive and emotional disturbances that contribute to major preventable causes of global disease burden. This study examines detailed personality profiles of underweight, normal, and overweight individuals to provide insights into the causes and treatments of abnormal weight., Methods: More than half of the population from four towns in Sardinia, Italy (n = 5693; age = 14-94 years; mean +/- standard deviation = 43 +/- 17 years) were assessed on multiple anthropometric measures and 30 facets that comprehensively cover the five major dimensions of personality, using the Revised NEO Personality Inventory., Results: High Neuroticism and low Conscientiousness were associated with being underweight and obese, respectively. High Impulsiveness (specifically eating-behavior items) and low Order were associated with body mass index categories of overweight and obese, and with measures of abdominal adiposity (waist and hip circumference). Those scoring in the top 10% of Impulsiveness were about 4 kg heavier than those in the bottom 10%, an effect independent and larger than the FTO genetic variant. Prospective analyses confirmed that Impulsiveness and Order were significant predictors of general and central measures of adiposity assessed 3 years later., Conclusions: Overweight and obese individuals have difficulty resisting cravings and lack methodical and organized behaviors that might influence diet and weight control. Although individuals' traits have limited impact on the current obesogenic epidemic, personality traits can improve clinical assessment, suggest points of intervention, and help tailor prevention and treatment approaches.

Potential founder population effects on personality trait means and variances were examined in a large, genetically homogeneous sample (N=5,669) from the Ogliastra, an isolated region within Sardinia, Italy. The Italian version of the Revised NEO Personality Inventory showed good psychometric properties: Internal consistency reliabilities ranged from 0.80 to 0.87; the factor structure replicated the American normative structure; and associations with education and gender replicated cross-cultural patterns. The hypothesis that mean trait levels in the Sardinian founder population would differ from mainland Italian values was not supported. Phenotypic variation in this founder population was within the range found in other cultures. However, the hypothesis of restricted phenotypic variation was supported for all five factors and 28 of the 30 facets when a Sardinian subsample matched on age, sex, and education was compared to a mainland Italian sample. The genetic homogeneity effect on the phenotypic expression of complex traits merits further exploration.

Both cross-sectional and longitudinal studies in the United States have shown consistent changes between college age and middle adulthood. There appear to be declines in 3 of the 5 major factors of personality--Neuroticism, Extraversion, and Openness--and increases in Agreeableness and Conscientiousness. To examine cross-cultural generalizability of these findings, translations of the Revised NEO Personality Inventory were administered to samples in Germany, Italy, Portugal, Croatia, and South Korea (N = 7,363). Similar patterns of age differences were seen in each country, for both men and women. Common trends were also seen for the more specific traits that define the major factors. Because these nations differ substantially in culture and recent history, results suggest the hypothesis that these are universal maturational changes in adult personality.