A potential link between gambling addiction severity and central dopamine levels -- evidence from spontaneous eye blink rates in gamblers and controls
Accumulating evidence points at similarities between substance use disorders and pathological gambling on the behavioral and neural level. In substance addiction, dysregulation of striatal dopamine transmission has been consistently revealed. Due to the neurotoxicity of stimulating substances, it is still debated if this constitutes mainly a consequence of recurrent substance abuse or a vulnerability marker for addiction disorders. For gambling addiction, no clear association with striatal dopamine levels has been unveiled so far. With its presumably negligible dopaminergic toxicity, possible differences in striatal dopamine transmission in gambling addiction might therefore constitute a vulnerability marker. Spontaneous eye blink rate (sEBR) is controversially discussed as a potential proxy measure for striatal dopamine levels. Here we examined sEBR in 21 male problem gamblers and 20 healthy control participants. In addition, participants completed a screening questionnaire for overall psychopathology and self-reported measures of alcohol and nicotine consumption. We found no significant difference in sEBR between gamblers and controls. However, in gamblers, sEBR was negatively associated with addiction severity and positively associated with psychopathology. A final exploratory analysis revealed that healthy controls with low sEBR displayed higher alcohol and nicotine consumption than healthy participants with high sEBR. Although the association between dopamine transmission and sEBR is still debated, our findings reveal that sEBR is sensitive to inter-individual differences in addiction severity in problem gamblers.