In many ways, the things we do and the experiences we have shape who we are – from our personality to the state of our mental health. But an equally important, if not more elusive, force that shapes us is our genes.
Now, in a vast genetic dragnet, researchers have pinpointed six sections of the human genome associated with key personality traits: extroversion, neuroticism, agreeableness, conscientiousness and openness to experience. And some of those bits of DNA could help determine not only whether we’re talkative or cautious, but also whether we’re predisposed to psychiatric disorders, such as schizophrenia and attention-deficit hyperactivity disorder (ADHD). Specifically, the researchers found links between extraversion and ADHD, neuroticism with depression, and openness with schizophrenia and bipolar disorder.
The findings open the door to a better understanding of such mental disorders, plus the possibility of better ways to identify and treat them.
The study, led by researchers at the University of California, San Diego and published in natural genetics, involved sifting through 60,000 genetic samples collected by consumer genomics company 23andMe. Researchers also sifted through genetic samples from a dataset from the Genetics of Personality Consortium, which contained data from about eighty thousand participants. With all the data combined, the researchers looked at the genetic blueprints for correlations between specific DNA traits, personality traits and mental disorders.
When psychologists consider personality traits, they often focus on the five main traits listed above. Scientists can score each person’s personality based on subscores for those traits. A previous study of twins and families suggested that about 40 percent of the variation on such personality tests can be explained by genetics.
Linking all the genetic and personality data together, the researchers found a strong association between neuroticism and a region of the genome called 8p23.1, which codes for genes related to innate immunity and the nervous system. This region has been linked to cancer and developmental neuropsychiatric disorders in previous research. So it is interesting that this same region is associated with the personality trait of neuroticism, which is typically characterized by anxiety, depression, and lack of emotional stability.
The study also found a strong association between extraversion and the gene region called 12q23.3. In previous studies, scientists linked this region to bipolar disorder, suggesting it could play an important role in regulating personality and temperament.
In correlation tests, the researchers found significant genetic correlations between neuroticism and depression, as well as between extroversion and ADHD. The authors suggest that this finding may indicate that ADHD could be a variant of extraversion.
The authors also found that a gene variant known as L3MBTL2 was associated with both neuroticism and schizophrenia, supporting known population-level findings of associations between neuroticism and schizophrenia. In addition, gene variant MTMR9 was found to be associated with both extroversion and sensitivity to antipsychotic drugs.
Finally, the authors saw non-statistically significant correlations between genes associated with conscientiousness, education level and academic high achievement.
Overall, the researchers concluded that there are shared genetic influences between personality traits and psychiatric disorders. Although the study was large, the authors note that their sample size didn’t give them enough statistical power to detect many rare genetic traits that could help explain personality and psychiatric outcomes. However, despite the limitations, the findings suggest that more research into the genetic relationship between personality traits, psychiatric disorders and gene variants could be beneficial.
Natural genetics2016. DOI: 10.1038/ng.3736 (About DOIs).