The goal of this clinical trial is to determine if active transcranial direct current stimulation (tDCS) plus varenicline is an effective, safe and accessible treatment option for smoking cessation. The main questions this trial aims to answer are:
1. Does active tDCS plus varenicline improve short-term and long-term smoking abstinence rates compared to sham tDCS plus varenicline?
2. Are the safety profiles between active tDCS plus varenicline and sham tDCS plus varenicline different?
The tDCS treatment schedule includes 10 daily sessions for the first 2 weeks (M to F), followed by 5 single bi-weekly booster sessions for the remainder of the treatment period. Participants will come in-person for two follow-up sessions to assess smoking behaviour at 6- and 12-months post-treatment.