Your DNA Reveals Less About Personality Than a Short Online Quiz, Largest Study Finds

A short online personality quiz, taking three to five minutes, tells you more about who you are than your entire genome does. That is the blunt takeaway offered by one of the researchers' own colleagues after a new study in Nature, which ranks among the largest genetic analyses of personality ever completed.

The work focuses on the 'big five' traits that psychology has used for decades to sort human temperament: openness to experience, which covers curiosity and imagination; conscientiousness, meaning organisation and responsibility; extraversion, or sociability; agreeableness, or compassion; and neuroticism, a tendency toward anxiety and volatility. A global team drew on data from up to 1.14 million participants across 46 study cohorts. Each person first completed a validated questionnaire, which gave them a score on each of the five traits.

The researchers then ran a genome-wide association study, scanning the DNA for tiny differences that turned up more often in people with higher or lower scores. Mani Ramaswami, professor of neurogenetics at Trinity College Dublin, said the study identified some 1,250 DNA variations associated with personality traits. He stressed that these are small changes in the DNA, not whole genes, and that each one on its own has a minuscule effect on behaviour. The aim was never to locate a single stretch of DNA that makes someone outgoing or anxious, but to find patterns spread across the genome that, added together, track small differences across large numbers of people.

The result reinforces an old idea in genetics: there is no single 'personality gene'. The dataset also directly challenged older theories that tried to tie traits to particular brain chemicals. The team combined the scattered variants into a single number, a polygenic index, and compared those scores with large public datasets on health, behaviour and social outcomes. Genetic patterns linked to higher conscientiousness went with lower body mass index, fewer hospital visits and lower substance use. Those linked to neuroticism showed strong associations with anxiety, depression and other psychiatric disorders. By middle age, people whose profiles pointed to higher openness were more likely to have moved into cosmopolitan professional areas, while those with higher conscientiousness profiles were more likely to have moved away from them toward affluent suburban communities.

None of this makes the index a crystal ball. Michel Nivard, professor of genetic epidemiology at the University of Bristol, said that for an individual the genetic effect is weak and adds no information over a three-to-five-minute test. Its value lies at the level of groups, he said, where it is strong enough to support new kinds of psychological, biological and social science working with averages across many people.

Causation is also unsettled. Hemant Tiwari, professor of biostatistics at the University of Alabama at Birmingham, cautioned against concluding that a neurotic personality causes depression. Shared genetic influences, he said, can affect personality, psychopathology, cognition, self-regulation and health at the same time, so the same genes may shape both temperament and health problems rather than one driving the other. Because the data cannot reliably separate the two, he said, whether personality itself causally drives later outcomes remains unresolved. Veena Kumari, professor of experimental psychology at Brunel University London, noted that the consistency of genetic signals across contexts supports a biological basis for traits such as extraversion and neuroticism, but that personality is a complex phenotype that may not be expressed or measured with the same precision across different walks of life.

To separate nature from nurture, the researchers compared siblings, who share an upbringing but inherit different combinations of DNA. The results largely rule out the possibility, in Nivard's words, that extraverted parents environmentally cause their children to be more extraverted.

A major limit remains: the genomic databases behind the work are dominated by people with European-like genomes, and a polygenic index built on them generally predicts less reliably in other ancestries. Ramaswami said sequencing DNA within families that show extreme behavioural variants will be far more useful than broad population studies. He noted that such an approach is already being pioneered in India for psychiatric conditions, in a joint effort between the NCBS and NIMHANS, both in Bengaluru.