Steep delay discounting, or a greater preference for smaller-immediate rewards over larger-delayed rewards, is a common phenomenon across a range of substance use and psychiatric disorders. Non-substance behavioral addictions (e.g., gambling disorder, internet gaming disorder, food addiction) are of increasing interest in delay discounting research. Individual studies have reported steeper discounting in people exhibiting various behavioral addictions compared to controls or significant correlations between discounting and behavioral addiction scales; however, not all studies have found significant effects. To synthesize the published research in this area and identify priorities for future research, we conducted a pre-registered systematic review and meta-analysis (following PRISMA guidelines) of delay discounting studies across a range of behavioral addiction categories. The final sample included 78 studies, yielding 87 effect sizes for the meta-analysis. For studies with categorical designs, we found statistically significant, medium-to-large effect sizes for gambling disorder (Cohen’s d = 0.82) and IGD (d = 0.89), although the IGD effect size was disproportionately influenced by a single study (adjusted d = 0.53 after removal). Categorical internet/smartphone studies were non-significant (d = 0.16, p = 0.06). Aggregate correlations in dimensional studies were statistically significant, but generally small magnitude for gambling (r = 0.22), internet/smartphone (r = 0.13) and food addiction (r = 0.12). Heterogeneity statistics suggested substantial variability across studies, and publication bias indices indicated moderate impact of unpublished or small sample studies. These findings generally suggest that some behavioral addictions are associated with steeper discounting, with the most robust evidence for gambling disorder. Importantly, this review also highlighted several categories with notably smaller effect sizes or categories with too few studies to be included (e.g., compulsive buying, exercise addiction). Further research on delay discounting in behavioral addictions is warranted, particularly for categories with relatively few studies.

DNA methylation allows for the environmental regulation of gene expression and is believed to link environmental stressors to psychiatric disorder phenotypes, such as anorexia nervosa (AN). The oxytocin receptor (OXTR) gene is epigenetically regulated, and studies have shown associations between OXTR and social behaviours in various samples, including women with AN. The present study examined differential levels of methylation at various CG sites of the OXTR gene in 69 women with active AN (AN‐Active), 21 in whom AN was in remission (AN‐Rem) and 35 with no eating disorder (NED). Within each group, we explored the correlation between methylation and measures of social behaviour such as insecure attachment and social avoidance. Hypermethylation of a number of CG sites was seen in AN‐Active participants as compared with AN‐Rem and NED participants. In the AN‐Rem sample, methylation at CG27501759 was significantly positively correlated with insecure attachment (r = .614, p = .003, permutation Q = 0.008) and social avoidance (r = .588, p = .005, permutation Q = 0.0184). Our results highlight differential methylation of the OXTR gene among women with AN, those in remission from AN, and those who never had AN and provide some evidence of associations between OXTR methylation and social behaviour in women remitted from AN.

Objective: Binge eating and associated eating disorders are characterized by abnormalities in reward processing. One component of reward is willingness to expend effort to obtain a reinforcer. The Effort Expenditure for Rewards Task (EEfRT) is a widely used behavioral measure of willingness to work for money. We sought to modify the EEfRT to examine willingness to work for food reward and to preliminarily examine the association between binge eating and effort expenditure for food.Method: Participants were 63 females recruited to span the spectrum of binge-eating severity.The modified EEfRT required participants to make a series of choices between an easier, low-reward option (one portion of food) and a harder, high-reward option (between two to five portions of food). Each trial also varied on probability of winning.Results: Participants self-reported engagement in the task, working hard at easy and hard tasks, and making choices based on reward probability and magnitude. As with the original EEfRT, probability, reward magnitude, and their interaction predicted the likelihood of choosing the hard task. Across two different measures, binge-eating symptoms interacted with reward magnitude, such that those with high binge eating used reward magnitude more to make trial choices than those with low binge eating.Discussion: These data provide initial support for the validity of the EEfRT modified for food as a behavioral measure of willingness to work for food reward. The impact of binge eating on effort expenditure must be replicated in samples of patients with eating disorders.

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