Tobacco cessation among smokers under substance use treatment for alcohol and/or cannabis: study protocol and pilot study.

The results of S1 were used to develop the questionnaires. S2 required some adjustments due to the COVID-19 pandemic, particularly the follow-up interviews being conducted by phone instead of face-to-face, and the recruitment rhythm was lower than expected. Recruitment will last until reaching at least 200-250 users. The fieldwork could not have been possible without the collaboration of the ACT-ATAC team and the introduction of several strategies. Trial registration The ACT-ATAC project has been successfully registered at Clinicaltrials.gov [NCT04841655].