Human platelets are an accessible source of monoamine oxidase (MAO). Platelet MAO levels have been consistently related to certain personality traits such as sensation-seeking behavior and impulsivity. Furthermore, low platelet MAO levels have been found in association with risky behaviors.

Because there was no previous investigation of MAO activity in pathological gambling, a disorder characterized by risky sensation-seeking behavior, (Carrasco et al. 1994) designed a study to examine it. The study measured platelet MAO activity in a group of pathological gamblers and its relation to sensation-seeking and impulse control.

Subjects of the study were fifteen male pathological gamblers from the outpatient clinic of a Madrid hospital. Control subjects were 25 healthy males. Subjects completed the Hamilton Anxiety and Depression Rating Scales and Zuckerman's Sensation Seeking Scale. Platelet MAO activity was determined using samples of the patients' blood.

The results show that in the group of pathological gamblers MAO activity was significantly lower than that in the control group. Gamblers also scored significantly lower in the sensation-seeking subscales than the control group. (This means they are more sensation-seeking than the controls. ) Platelet MAO activity showed a positive trend of correlation with high senation-seeking. In other words, the greater the sensation-seeking, the lower the MAO activity.