Past research has indicated an association between impulsivity and drug abuse, but the exact role played by this personality trait has remained unclear. Specifically, researchers have been unsure if impulsivity stems from drug use or precedes it. In a new study from the June issue of Science, researchers from the University of Cambridge attempted to answer this question by examining the relationship between addiction and two closely-related personality traits— impulsivity and novelty-seeking. Their results point toward impulsivity as especially influential in the development of addiction.

The researchers used animal models to compare the two personality traits, breeding rats to display certain characteristics. Highly impulsive rats were defined as those that, when trained to give a response after a specific cue, often responded before the cue, while novelty-seeking rats were those that behaved curiously and without caution when placed in a new environment. Both groups were provided with cocaine and allowed to control their intake of the substance. Based on the researchers’ early observations, a novelty-seeking personality may contribute to an individual’s initiation of drug use, as rats from this group self-administered cocaine more quickly and in higher amounts than impulsive rats. Novelty-seeking did not lead to long-term use, however, and after 40 days, these rats had mostly decreased their use of the drug. An association between impulsivity and addiction had emerged by this time, however, and the impulsive rats consistently self-administered cocaine, even when doing so resulted in an electric shock.

These findings support research that was published last year by Dr. Jeffrey Dalley, who also worked on this current study. Using rats, Dr. Dalley found a connection between impulsivity and a neurological variation that has been linked to drug abuse— low levels of dopamine receptors. Further testing revealed that impulsive rats also self-administered greater amounts of cocaine than controls, and taken together, these results indicate that the dopamine system may have an effect on both impulsivity and addiction. By further investigating whether or not personality traits influence drug use, the researchers of this current study provide more evidence that impulsivity can contribute to dependence. Additionally, as one of the study’s authors, Professor Barry Everitt, explained in a press release, they have demonstrated how an addiction might develop: “This study is important because it shows that impulsivity is a vulnerability characteristic that predicts a switch to compulsive drug use when individuals are exposed to and take cocaine. Therefore, drug addiction is characterized by a shift from impulsive to compulsive behavior.”

For some individuals, casual drug use never leads to dependency, but others struggle with addiction soon after their first experience with a drug. As we gain further knowledge of the factors that influence drug use and dependency, we may be able to predict those who will be most at risk for addiction and develop more effective treatment options for these individuals. By addressing impulsive behavior, for instance, we may also be able to address an associated vulnerability to addiction.