Success in giving up smoking can be improved through social support, problem solving or skills training, and various drugs. A combination of drugs and other treatments is most effective.1 Drugs include nicotine replacement products, varenicline (Champix), and bupropion (Zyban and generics). Varenicline and bupropion inhibit the craving to smoke through unknown mechanisms. Both drugs influence the dopamine system, which regulates cognition, mood, and behaviour.2 Both varenicline and bupropion have been associated with “changes in behaviour, agitation, depressed mood, suicidal ideation, and attempted and completed suicide” in patients who had no psychiatric history and were not taking psychotropics.3 4 Nicotine replacement products have no such known associations.3 In the linked study (doi:10.1136/bmj.b3805), Gunnell and colleagues report the first retrospective cohort study to examine suicidal thoughts and behaviours after exposure to smoking cessation products.5

In the United States, changes to labelling of varenicline have been based on biological plausibility and voluntary spontaneous reports, which represent …