Effect of Cannabis on Cigarette Use Behavior

Who May Qualify: 1. Healthy non-treatment seeking adults aged 21 or older 2. Report daily use of combustible tobacco cigarettes 3. Biological confirmation of cigarette use: have an expired carbon monoxide (CO) level of more than 5 ppm and a positive urine cotinine test at screening 4. Report current use of cannabis (at least 1 occasion per week) 5. Have experience with the inhalation route of administration for cannabis 6. Biological confirmation of cannabis use: have a positive urinary THC drug test at screening. 7. For women of children bearing potential and men with female partners of child-bearing potential, must be willing to use an effective form of contraception during the study. Who Should NOT Join This Trial: 1. Report current intention to reduce or quit cannabis or tobacco use within the next 30 days 2. Meet Diagnostic and Statistical Manual (DSM-5) criteria for a substance use disorder other than alcohol, cannabis, or nicotine 3. Test positive for illicit drugs other than cannabis and tobacco 4. Positive breath alcohol test at study admission 5. Have a current physical or mental illness judged by the study team to negatively impact participant safety or scientific integrity 6. Have a lifetime history of suicidal behavior (i.e. past suicide attempt), or current suicidal behavior or ideation as assessed by the Columbia Suicide Severity Rating Scale (C-SSRS) 7. Are currently pregnant, planning to become pregnant in the next three months or are currently breastfeeding 8. Have a history of clinically significant cardiac arrhythmias or vasospastic disease (e.g., Prinzmetal's angina) 9. Are currently enrolled in another clinical trial or have received any drug as part of a research study within 30 days of study participation. Always talk to your doctor about whether this trial is right for you.