Huge genetic study finds strong links between DNA and personality traits

Personality is something we all share, but the different ways we think and feel also make us unique. Personality is relatively stable and influences nearly every aspect of human life, from academic performance and career choices to health behaviours and longevity. For example, someone who is responsible might avoid taking risks or alcohol and drug use. Our new study, published in Nature, has linked personality with more than 1,200 common genetic variants, highlighting its central role in understanding human experience. This was only possible because 1.14 million people contributed their DNA and time to 46 research studies in 13 countries that measured personality in the same way. How did we measure personality? Scientists summarise thousands of personality traits with five relatively independent factors called the Big Five: extraversion – being sociable, assertive, and energetic agreeableness – being compassionate, cooperative, and respectful conscientiousness – being responsible, productive, and organised neuroticism – being emotionally reactive, anxious, and depressive openness to experience – being curious, imaginative, and preferencing variety. You might be familiar with the Myers-Briggs or Enneagram personality type systems, which are different ways to describe personality. Scientists prefer the Big Five because they describe personality on a continuous spectrum rather than sorting people into discrete types. How scientists study the genetics of personality Genetics were first linked to personality through studies of twins, which show that closely related people tend to be more similar in their personalities. Today, researchers use a method called a genome-wide association study, or GWAS, to find differences in genetic markers by comparing the DNA of many people at once. In this study, researchers from 15 countries around the world, including our team at QIMR Berghofer, conducted up to five GWASs on their own study data. We were searching for common genetic variants linked to each personality trait. We then merged these individual GWAS results into a combined analysis, led by the Revived Genomics of Personality Consortium from Michigan State University. This substantially boosted our ability to find genetic markers related to personality. Follow-up tests looked at which genes those markers are associated with. We also wanted to know where in the body these genes are active, and how the genetics of personality compares to other behavioural traits. What did we find? We found 1,260 genetic markers associated with the Big Five, including 824 not found in previous studies. Between 5 and 16% of variation in personality can be explained by common genetic variants. A similar result has been found for major depression. This suggests genetics plays a robust role in creating personality. At the same time, a large proportion is also affected by our environment. However, this isn’t due to a shared family environment. You don’t have a similar personality to your family members because you grew up together. We tested this by comparing GWAS results from unrelated people and family members. If shared family environment were biasing the results, we would expect to see differences between the GWAS results from unrelated people, and family members. This bias is seen in studies of educational attainment and cognitive performance. We didn’t find evidence of this for the Big Five. Personality seems to be distinct from these other behavioural outcomes. The genetic markers associated with each Big Five trait, except agreeableness, were strongly linked to genes expressed in the prefrontal cortex of the brain. This area, located right behind your forehead, is often called the brain’s “personality centre”. It is important for emotional regulation, decision-making and self-control. The prefrontal cortex is also implicated in many psychiatric disorders including anxiety, schizophrenia, attention deficit hyperactivity disorder (ADHD), and bipolar disorder. The Big Five and psychiatric disorders show substantial genetic sharing, which may explain why they are consistently linked to the same brain region. Overlapping genetic signals between personality and health traits show how personality can also directly affect our physical health. For example, extraversion increased COVID infection risk. Conscientiousness decreased body-mass index (BMI), reduced the likelihood of smoking and reduced the frequency of spells in hospital. The genetics of personality also plays a major role in how people complete surveys for research studies. For example, those scoring high for agreeableness and openness to experience are more likely to complete optional questionnaires. Therefore, the genetics of personality may influence published research results based on survey data in ways that are unaccounted for. What’s next? These results give us more insight into the genetics of personality than has been possible in the past. However, there are still a number of gaps to explore in the future. The genetics of the Big Five were highly consistent across geography, age group, and personality measure for these studies. But the Big Five aren’t necessarily the best summary of personality differences across all cultures and languages. This means our results may not apply to everyone in the world. Personality is a fundamental aspect of being human. These research findings have overhauled our understanding of genetic effects on personality, and how personality relates to many aspects of our lives. In time, personality traits can be integrated into models for both physical and mental health outcomes. This will open new opportunities to improve how we categorise, identify, and treat disease.