PET, fMRI find psychopaths have higher dopamine levels

High dopamine levels are linked to a greater level of such psychopathic traits as manipulativeness, egocentricity, aggression, and risk-taking, a study by Vanderbilt University researchers has found.

Using PET and fMRI studies, the researchers looked for changes in the dopamine reward circuitry. They also had all participants complete a personality inventory to assess their tendencies to psychopathic behavior.

After volunteers were given a dose of amphetamine, they were scanned with PET to measure dopamine release. Substance abuse has been shown in the past to be associated with alterations in dopamine responses; the researchers hypothesized that psychopathic traits were also linked to dysfunction in dopamine reward circuitry.

“Consistent with what we thought, we found people with high levels of psychopathic traits had almost four times the amount of dopamine released in response to amphetamine,” said Joshua Buckholtz, a graduate student in psychology and lead author of the study.

In the fMRI portion of the test, volunteers were scanned while told they would receive a monetary reward for completing a simple task. The dopamine reward area was more active in subjects with elevated psychopathic traits than in other volunteers while subjects anticipated the monetary reward.