RESUMEN
BACKGROUND: The popularity of temporary abstinence challenges (TACs) concerning alcohol consumption is increasing. Support is found to be essential for participants to help them get through a challenge. This study aimed to evaluate the additional effect of a self-help guide, based on health behaviour theories and behaviour change techniques, on (i) successful completion of a TAC and (ii) changes in drinking refusal self-efficacy (DRSE), behavioural automaticity, craving, and alcohol consumption. METHODS: A randomized controlled trial was performed (OSF registries: OSF.IO/B95VU). NoThanks participants received a questionnaire before the TAC (T0) and 8 months after the TAC (T1). Out of a subgroup of 1308 respondents who were interested in additional support, 652 were randomly assigned to receive the guide (experimental group), and 656 did not receive any additional support (control group). Logistic regressions and (generalized) linear mixed model analyses were used. RESULTS: After 8 months, all participants showed a significant decrease in behavioural automaticity, craving, and alcohol consumption, irrespective of group assignment. No significant changes were observed in the DRSE. This degree of change over time in behavioural automaticity, craving, and alcohol consumption did not differ between the experimental and control group. Sensitivity analyses with participants in the experimental group, who differed in exposure to the guide, did not show differences either. CONCLUSION: The self-help guide, and how it was designed, added no value to the TAC. Future research should focus on more bottom-up, customized support and explore what (different subgroups of) participants think they need as extra support during a TAC.