Relatively strong automatic appetitive action-tendencies in male carriers of the OPRM1 G-allele

This study investigated whether automatic approach action tendencies for alcohol-related stimuli were associated with variation in the mu-opioid receptor gene (OPRM1), previously related to rewarding effects of alcohol and craving. An adapted approach avoidance task was used, in which participants pulled or pushed a joystick in reaction to the format of a picture shown on the computer screen (e.g. pull landscape pictures and push portrait pictures). Picture size on the screen changed upon joystick movement, so that upon a pull movement picture size increased (creating a sense of approach) and upon a push movement picture size decreased (avoidance). Participants reacted to four categories of pictures: alcohol-related, other appetitive, general positive and general negative. The sample consisted of 84 heavy drinking young men without a g-allele in the A118G (or A355G) single nucleotide polymorphism of the OPRM1 gene and 24 heavy drinking young men with at least one g-allele. Heavy drinking carriers of a g-allele showed relatively strong automatic approach tendencies for alcohol (approach bias). Unexpectedly, they also showed an approach bias for other appetitive stimuli. No approach bias was found for general positive or negative stimuli. These results suggest that automatic approach tendencies in response to appetitive stimuli could play a role in the etiology of addictive behaviors and related disorders. Further research is needed to investigate the specificity of this approach bias and possible gender differences.