UCLA Study Establishes Genetic Link to Thrill-Seeking Personality Types


Date: July 7, 1998
Contact: Jacquie Michels ( jacquiem@support.ucla.edu )
Phone: (310) 206-1960

Our genetic makeup may predispose us to certain personality traits or patterns of behavior, a new UCLA study suggests. Variant forms of two key genes, the DRD2 and DRD4 dopamine receptor genes, may play a role in causing and maintaining certain aggressive, impulsive personality types and reinforcing the associated thrill-seeking behaviors. The study, led by Dr. Ernest Noble of the UCLA School of Medicine, was published in the American Journal of Medical Genetics.

Noble and colleagues previously demonstrated that the DRD2 gene links to certain types of addictive and abusive behaviors such as alcohol abuse, drug abuse, smoking and overeating. Individuals who express these genetic variants or alleles have fewer dopamine receptors in their brains to record sensations of pleasure and satisfaction. These individuals may, therefore, be driven to overindulge in substances or activities that stimulate their existing receptors and give them pleasure levels comparable to people who have a more standard number of pleasure receptors.

For the current study, the researchers evaluated 119 boys averaging 12 years of age who had not yet used alcohol or other drugs of abuse. Each subject underwent a genetic screening and a standardized personality assessment (the Tridimensional Personality Questionnaire which measures three dimensions of temperament).

The researchers found a marked correlation between behavior patterns which they term "novelty seeking" and the expression of certain variants of the DRD2 and DRD4 dopamine receptor genes. Novelty-seeking behavior markers include excitability, impulsiveness, extravagance and disorderliness.

"Identification of the molecular genetic factors contributing to temperament and personality is highly complicated, and we are just beginning to put the many pieces of this puzzle together," said Noble, Pike Professor of Alcohol Studies and a professor of psychiatry and biobehavioral sciences at UCLA. "Despite the considerable evidence supporting the role of the dopamine receptor genes to pleasure and thrill-seeking behaviors, I believe as many as eight additional genes may be involved in forming and supporting personality characteristics."

According to Noble, certain personality characteristics are known to be related to the body's dopaminergic system, as is predisposition to abuse certain substances. "Now we are making a link between the two," he said. "People may be born with abusive tendencies, and these may be detectable as personality traits well before they take their first drink or puff of a cigarette. If we could predict who would become a substance abuser, we could potentially provide early intervention that would help these individuals make appropriate and active choices about their lives.

"About half of an individual's personality relates to genetics and half to environment including upbringing, education and the influence of role models. But clearly, the genes we are born with are just as important as the lessons our parents teach us," Noble added. "So there is no clear slate at birth. The architecture for what we will become is already in place well before we are born. Parents should only take part of the credit, and only part of the blame, for the kind of people their children become."

Girls are just as likely as boys to demonstrate thrill-seeking behaviors as a result of their genetic makeup, Noble stated. Subsequent studies will follow children of both sexes in an effort to demonstrate the reliability of combined genetic screening and behavioral testing as predictive tools for addictive behavior.

JM319