In the investigators previous analysis using CPRD data the age- and sex-adjusted hazard ratio for self-harm/suicide for varenicline vs. nicotine replacement therapy at nine months was 0.73 (95% CI: 0.54 to 0.99); after adjusting for possible confounders this became: 0.90 (95% CI: 0.66 to 1.22). A 70% increase in sample size would lead to a reduction of the standard error by a factor of 1.3, reducing the breadth of the above-adjusted confidence interval from 0.56 to 0.43.