Holmes and colleagues examined the variability in brain structure among 1,234 males and females aged 18 to 35 with no history of psychiatric disorders or substance dependence. Using magnetic resonance imaging (MRI), the team measured the size of particular regions of the brain for each participant. The participants also completed questionnaires assessing traits associated with sensation-seeking and impulsivity such as their need for novel and intense experiences, willingness to take risks, and a tendency to make rapid decisions. The participants also reported alcohol, tobacco, and caffeine usage.
They found that people who reported seeking high levels of stimulation or excitement had reduced cortical thickness, or gray matter, in brain regions associated with decision making and self-control. The strongest links occurred in brain areas related to the ability to regulate emotions and behavior, the anterior cingulate and middle frontal gyrus. Changes in those brain structures also correlated with participants’ self-reported tendency to act on impulse and with heightened use of alcohol, tobacco, or caffeine.