A Critical Review of Front-loading: A Maladaptive Drinking Pattern Driven by Alcohol's Rewarding Effects

This paper is now published open-access at Alcoholism: Clinical and Experimental Research: https://onlinelibrary.wiley.com/doi/10.1111/acer.14924. Front-loading is a drinking pattern where intake is skewed toward the onset of reward access. This phenomenon has been reported across several different alcohol self-administration protocols using a wide variety of species, including humans. The hypothesis of the current review is that front-loading emerges in response to the rewarding effects of alcohol and can be used as a measure of motivation to consume alcohol. Alternative or additional hypotheses for what front-loading may represent are considered and contrasted with the main hypothesis that: 1) front-loading is directed at overcoming chronic and/or metabolic tolerance and 2) front-loading is driven by negative reinforcement. Evidence for each of these explanations is reviewed. We also consider how front-loading has been evaluated statistically in previous research and make recommendations for defining this intake pattern in future studies. Because front-loading may predict long-term maladaptive alcohol drinking patterns leading to the development of alcohol use disorder (AUD), several future directions are proposed to elucidate the relationship between front-loading and AUD.