Lastly, half of the trials were sponsored by Pfizer, the manufacturers of varenicline. Although previous research with nicotine replacement therapy has shown that industry sponsored trials were more likely than other trials to report outcomes that were favourable to the study sponsor,14 we did not find any evidence for differences in depression and suicidal ideation for industry versus non industry sponsored trials (P=0.386 and P=0.380, respectively, for interaction). In addition, all of the industry sponsored trials were assessed overall as having a low risk of bias.
