Background and aim:
There is a lack of research on the stress-related transfer from goal-directed behavior to stimulus-response habits in (early stages of) online buying-shopping disorder (BSD). This study investigated the Pavlovian-to-instrumental transfer (PIT) effect after reward devaluation (PIT-dev) as indicator of habitual behavior and its modulation by acute stress in individuals with risky (online) buying-shopping (r-BSh).

Methods:
Individuals with r-BSh (n = 67) and a control group (n = 67) underwent a PIT paradigm with devaluation procedure. A stress induction/control procedure was administered after the first part of the paradigm. Four salivary samples (alpha-amylase, sAA; cortisol, sCort) and subjective stress ratings were collected before/after stress induction.

Results:
Individuals with r-BSh showed higher sAA levels (after stress induction), but comparable sCort and subjective stress levels to the control group. The devaluation reduced, albeit not abolished, shopping-specific instrumental behaviors in both groups, particularly in neutral trials. There were no interaction effects of stress condition, group and devaluation on shopping-specific response choice in the preregistered analysis. sCort response significantly predicted PIT-dev as indicator for habitual behavior. Exploratory analyses showed that interactions of BSD symptom severity with subjective and sCort stress response predicted PIT-dev.

Discussion and conclusions:
The findings are mixed. They show some evidence for a stress-related shift to habitual shopping-specific behaviors in persons with higher symptom severity yet they do not match findings of other planned analyses. Further research is needed to clarify the role of stress in PIT effects and potentially habitual behaviors, which may have implications for prevention/early intervention.