Brain Changes Linked to Combined Cannabis and Tobacco Use Offer Clues to Addiction

PET imaging has revealed the first evidence in humans of changes in brain chemistry among people who use both cannabis and tobacco. This finding could help guide the growth of new treatments for cannabis use disorder.

People who use both cannabis and tobacco show distinct brain differences compared to those who only use cannabis, according to a new study led by researchers from McGill University’s Douglas Research Center.

The revelation could help explain why people who consume both substances frequently enough experience higher levels of depression and anxiety, and why quitting cannabis tends to be more difficult for them than for those who do not use tobacco.

“This is the first evidence in humans of a molecular mechanism that may underlie why people who use both cannabis and tobacco experience worse outcomes,” said lead author rachel Rabin, Associate Professor in McGill’s Department of Psychiatry and researcher at the Douglas.

“Identifying this mechanism is an crucial step toward finding targets for future medications to treat cannabis use disorder, especially among those that co-use tobacco. Right now, the only available treatments are behavioral therapies such as counselling,” she said.

in Canada, about one in 20 people who used cannabis in the past year are considered at risk for cannabis use disorder. That number increases to one in three among those who use cannabis more frequently.