Upon starting medical school, I remember feeling amazed to learn just how many of my classmates had physician parents. I felt like I was in the minority, not having any family members of my own who were doctors. This made me realize: Physician parents tend to breed physician children. But why? I soon discovered that the answer may lie in the genetics of personality.
The academic study of personality has grown extensively over the course of the past century. Moreover, the topic has captured public attention as well, and a current Google search for “personality” shows over 331,000,000 results. Personality traits also play a critical role in understanding human behavior and decision-making. Accordingly, current research suggests there may be a substantial heritable component to personality traits.
The Merriam-Webster Dictionary defines “personality” as a set of distinctive traits and characteristics that relate to a particular person. These traits are stable across time, as the structure of personality traits shows consistency across different groups of people in various cultures. Large, well-conducted studies have indicated genetic contributions to personality and human behavior. Scarr and McCartney have even been suggested that personality driven by genotype determines the choices we make.
Adoption studies have also been useful in studying personality, as in the case of parents who have biological as well as adopted children and provide the family environment for both types, yet share genes only with the biological. Loehlin analyzed data from three adoption studies in which children were adopted away at an early age and where adults and grown-up children were given the same personality scale, namely the Eysenck Personality Questionnaire and Inventory. Loehlin found that children resemble their biological parents but not their adoptive parents. In other words, personality was found to be heritable.
Additional research has found evidence for a heritable component in personality. Bouchard’s summary of data from Minnesota Study of Twins Reared Apart suggested broad heritabilities of big five personality dimensions ranging from about 30 percent for agreeableness to about 50 percent for neuroticism. Moreover, Plomin and Nesselroade suggested that heritability of personality changes over development, with higher heritability at older ages. Personality research has even infiltrated molecular genetics, and there now appear to be correlations between novelty seeking and variations at the D4 dopamine receptor gene. Furthermore, a link has been found between neuroticism and the neurotransmitter serotonin.
Medicine is known to attract competitive and overachieving personality types. Though many can successfully argue that physician parents create an environment in which their children are likely to become interested in medicine, the role of genetics should not be discounted. Ultimately, a strong body of evidence suggests that personality is heritable, and this may explain why so many physician parents tend to have physician children, as similar personalities are likely to be drawn to similar careers.
Perhaps Beatrix Potter was on to something when she said, “I hold that a strongly marked personality can influence descendants for generations.”
Robert Dorfman is a medical student.
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