Background and aims: Experiencing acute stress is common in behavioral addictions such as gambling disorder. Additionally, like most substance-induced addictions, aberrant decision-making wherein a reactive habit-induced response (conceptualized as a Model-free [MF] in reinforcement learning) suppresses a flexible goal-directed response (conceptualized as a Model-based [MB]) is also common in gambling disorder. In the current study we investigated the influence of acute stress on the balance between habitual response and the goal-directed system. Methods: A sample of N 5 116 problem gamblers (PG) and healthy controls (HC) performed an acute stress taskthe Socially Evaluated Cold pressure task (SECPT)or a control task. Self-reported stress and salivary cortisol were collected as measures of acute stress. Following the SECPT, participants performed the Two-Step Markov Task to account for the relative contribution of MB and MF strategies. Additionally, verbal working memory and IQ measures were collected to account for their mediating effects on the orchestration between MB/MF and the impact of stress. Results: Both groups had comparable baseline and stress-induced cortisol response to the SECPT. Non-stressed PG displayed lower MB learning than HC. MANOVA and regression analyses showed a deleterious effect of stress-induced cortisol response on the orchestration between MB and MF learning in HC but not in PG. These effects remained when controlling for working memory and IQ. Discussion and Conclusions: We found an abnormal pattern of modulation of stress on the orchestration between MB and MF learning among PG. Several interpretations and future research directions are discussed.

Loss-chasing, the tendency to continue and/or intensify gambling following losses, is a key clinical symptom in gambling disorder and a central feature in problem gambling, endorsed by at-risk problem gamblers. Despite its centrality, the extant literature has often operationalised loss-chasing across distinct behavioural expressions. The current systematic scoping review aimed to map the heterogeneous operationalisations of loss-chasing in the literature. The reviewed studies defined loss-chasing either between-sessions (n=39) or within-sessions (n=38), as a long-recognised distinction. For both categories, further behavioural expressions could be distinguished. Between-session loss-chasing was captured by endorsing an item ‘returning another day/time to recoup losses’, or behaviourally as the interval between successive sessions, or as increasing stakes on the next visit. Within-session loss-chasing was defined as continuing to gamble, and/or intensifying betting either by increased risk-taking, stake size, or speed of play. Additionally, much heterogeneity was observed in gambling contexts examined, the exact definition of loss, and the potential delineation of win-chasing. Open questions and future directions are discussed. Overall, this paper severs as a first step towards more conceptual clarity of loss-chasing.