We sought all placebo controlled randomised controlled trials of any duration in humans of varenicline at the maximum dose (1 mg twice daily) as described in the recommended standard titration regimen for varenicline (www.chantix.com). We included studies in smokers and non-smokers. We conducted searches of computer databases and online clinical trial registries (Medline, Embase, PsycINFO, the Cochrane Central Register of Controlled Trials (CENTRAL) and clinicaltrials.gov). The search strategy is shown in appendix 1. The searches were performed from the inception of each of the databases to 9 May 2014. There were no language restrictions. We manually searched reference lists of relevant research articles and previous systematic reviews.10 16
