Nature vs. nurture has been a long-standing argument between the fields of biology and psychology. However, new data from researchers at University of California San Diego (UCSD) School of Medicine scores some points for biologists, as investigators have identified six loci or regions of the human genome that are significantly linked to personality traits. Moreover, the new findings also show correlations with psychiatric disorders.
“Although personality traits are heritable, it has been difficult to characterize genetic variants associated with personality until recent, large-scale genome-wide association studies, or GWAS,” explained senior study investigator Chi-Hua Chen, Ph.D., assistant professor in the department of radiology at UCSD School of Medicine.
The findings from this study were published recently in Nature in an article entitled “Genome-Wide Analyses for Personality Traits Identify Six Genomic Loci and Show Correlations with Psychiatric Disorders.”
Five psychological factors are commonly used to measure individual differences in personality:
- Extraversion (versus introversion) reflects talkativeness, assertiveness, and a high activity level
- Neuroticism (versus emotional stability) reflects negative affect, such as anxiety and depression
- Agreeableness (versus antagonism) measures cooperativeness and compassion
- Conscientiousness (versus undependability) indicates diligence and self-discipline
- Openness to experience (versus being closed to experience) suggests intellectual curiosity and creativity.
Psychologists often define personality phenotypes based upon quantitative scoring of these five factors. Previous meta-analyses of twins and family studies have attributed approximately 40% of the variance in personality to genetic factors. GWAS, which looks for genetic variations across a large sampling of people, have discovered several variants associated with the five factors.
In the current study, the sample size of the meta-analyses was very large—123,132 to 260,861 participants in different studies. Yet, the investigators only used GWAS summary statistics and cannot estimate all genetic variance factors, so they urge caution in overinterpretation of the results.
The UCSD researchers analyzed genetic variations among the five personality traits and six psychiatric disorders using data from 23andMe, a privately held personal genomics and biotechnology company, the Genetics of Personality Consortium, a European-based collaboration of GWAS focusing on personality questions, UK Biobank, and deCODE Genetics, an Iceland-based human genetics company.
Interestingly, the researchers found that extraversion was associated with variants in the gene WSCD2 and near gene PCDH15—whereas neuroticism was associated with variants on chromosome 8p23.1 and gene L3MBTL2. Personality traits were largely separated genetically from psychiatric disorders, except for neuroticism and openness to experience, which clustered in the same genomic regions as the disorders.
Additionally, there were high genetic correlations between extraversion and attention-deficit hyperactivity disorder (ADHD) and between openness and schizophrenia and bipolar disorder. Neuroticism was genetically correlated with internalized psychopathologies, such as depression and anxiety.
“We identified genetic variants linked to extraversion and neuroticism personality traits,” Dr. Chen noted. “Our study is in an early stage for genetic research in personality and many more genetic variants associated with personality traits are to be discovered. We found genetic correlations between personality traits and psychiatric disorders, but specific variants underlying the correlations are unknown.”