Intervention
Participants were instructed to smoke their usual brand variant and length (king size or regular) of cigarettes from a single size of cigarette pack in each of the two intervention periods: (a) 20 cigarettes and (b) 25 cigarettes. Each intervention period lasted 14 days. Participants could smoke cigarettes of any brand variant and from either pack size in the ‘usual behaviour’ period, which lasted at least 7 days between the intervention periods.
