Could a Nicotine-Free cigarette break the habit?

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Age 19 years or older. * Current daily smoker of at least 10 conventional cigarettes per day for the past 12 months. Concurrent heated tobacco product use is permitted only when the participant meets the conventional-cigarette criterion and is a conventional-cigarette-dominant user. * No intention to quit smoking within the next month. * Willingness to switch entirely to the assigned study cigarettes during the trial period. * Ability to understand written Korean and complete study procedures independently. * Ability to use a smartphone for EMA data collection. * Ability to provide written informed consent. Exclusion Criteria: * Current regular use of electronic cigarettes (e-cigarettes). * Self-reported pregnancy, planning pregnancy during the study period, or breastfeeding; or positive pregnancy test at screening for participants who can become pregnant. * Current use of pharmacological smoking cessation aids, including varenicline, bupropion, or nicotine replacement therapy. * Serious psychiatric disorder that would interfere with study participation, such as psychosis or severe depression. * Any medical condition that contraindicates continued smoking, including prespecified safety thresholds such as systolic blood pressure of 160 mmHg or higher, heart rate of 105 beats/min or higher, or heart rate below 45 beats/min with symptoms. * Any other factor that may affect adherence or pose a health risk to the participant. * Inability to read and write sufficiently to complete study activities. * No reliable way for the research team to communicate with the participant by telephone or email. * Current participation in another tobacco- or nicotine-related research study. * Prior participation in a similar tobacco or nicotine intervention trial involving SPECTRUM research cigarettes or manipulation of cigarette nicotine content, if determined to affect eligibility.