A new study by researchers at McGill University has shown that people who use cannabis and tobacco simultaneously exhibit significantly different changes in their brains compared to those who only use cannabis.
This finding may explain why combined cannabis and tobacco users often report increased levels of depression and anxiety, and why they find it harder to quit cannabis use compared to those who only use cannabis.
The study’s authors note that this is the first evidence in humans of a molecular mechanism that may underlie the worse outcomes experienced by individuals who co-use cannabis and tobacco. The identification of this mechanism is an important step towards developing medications to treat cannabis use disorder.
PET brain scans revealed that the level of the FAAH enzyme was significantly higher in cannabis and tobacco users than in cannabis-only users. FAAH is an enzyme that breaks down anandamide—a natural molecule often called the “bliss molecule”—which is involved in the regulation of mood and stress.
A high level of the FAAH enzyme leads to a reduction in anandamide, which in turn is associated with anxiety, depression, and an increased risk of relapse when attempting to cease cannabis use.
The study analyzed data from 13 young adult participants. Eight of the participants were cannabis-only users, while five belonged to the group of simultaneous cannabis and tobacco users.
Although this data was initially collected as part of another research project, the researchers noted that the brain change observed was clear and differentiated compared to cannabis-only users. These study results suggest that the discovered changes are not caused solely by tobacco use.
