The DNA of two randomly selected people is approximately 99.9% identical. However, differences in the remaining 0.1% of the genome influence many individual traits, including appearance, disease risk, and the body's response to medications. A study by researchers at the University of Tartu found that this small amount of genetic variation may also be linked to several personality traits.
In a study published this week in Nature, researchers from the University of Tartu identified more than one thousand genetic variants associated with human behavioural traits. The paper is based on a study involving more than one million participants and sought to uncover possible links between DNA variation and differences in personality, focusing on five major personality traits: openness, conscientiousness, extraversion, agreeableness, and neuroticism.
Over the past century, numerous studies have shown that personality variation is influenced by both genetic and environmental factors. Identifying genetic markers associated with personality is challenging because many genes contribute to these traits, and the effect of any single genetic variant is extremely small. Consequently, uncovering reliable associations requires very large study populations.
In 2021-2022, the Estonian Biobank conducted a personality study involving nearly 80,000 participants. While this is a very large sample in the Estonian context, it is not sufficient for personality genetics research. Researchers from Tartu joined forces with 45 other international datasets to make the overall sample as representative as possible. As a result, data from as many as 1.1 million individuals could be used to analyse certain personality traits. The contribution of Estonian biobank participants stood out for both its size and depth: the Estonian sample was the third-largest, and personality was assessed using the most comprehensive questionnaire among all participating cohorts.
The results were remarkably consistent across different study groups, including participants of different ages and geographical backgrounds. However, the identified genetic variants explained only a small proportion of the differences in personality traits, approximately 4.8% to 9.3%. This suggests that environmental factors, social relationships, and life experiences, together with their interaction with genes, may have an even greater influence on the development of personality than genetic factors alone.
Others' Perspectives Confirm the Genetic Basis of Personality Traits
A unique feature of the Estonian Biobank personality study was that participants could ask someone they knew to evaluate their personality as well. "No other biobank in the world offers such an opportunity!" said Uku Vainik, Professor of Behavioural Genetics at the University of Tartu. Thanks to the distinctive design of the biobank's personality study, researchers were able to compare whether self-assessments and assessments provided by close acquaintances reflected the same genetic signal.
The results of the two assessment methods showed substantial overlap. This indicates that the genetics of personality do not merely reflect how individuals perceive themselves but also observable behavioural characteristics recognised by others. "This shows that measurable personality traits are truly real, publicly observable characteristics of people, rather than merely individuals' own opinions about themselves," explained René Mõttus, Professor of Personality Psychology and co-lead of the study.
Personality Influences More Than Just Social Skills
Now that researchers have gained an initial overview of the genetics of personality, new and exciting questions can be addressed. For example, Kerli Ilves, a junior research fellow, is investigating potential causal links between personality and health using genetic data. Preliminary findings suggest that personality traits play an important role in shaping health behaviours, influencing factors such as body weight, smoking tendencies, and alcohol consumption. Ilves has also identified associations in the opposite direction, where established behavioural patterns may themselves influence personality. "We especially see this kind of relationship in smoking," Ilves noted.
Researchers in Tartu emphasise that these findings are still preliminary. "The next step is to use other methods, such as longitudinal studies, to determine whether changes in personality are accompanied by changes in health behaviour, and vice versa," explained Vainik. To support this work, the Estonian Biobank is planning a future study on personality and cognitive functioning. A better understanding of the links between personality and health could help pave the way for more effective and person-centred approaches to supporting healthy behaviours.
