THCEffect of Cannabis on Cigarette Use Behavior

Inclusion Criteria:

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.

Exclusion Criteria:

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.