• Posted September 13, 2023

Depression Risk Rises in Folks Who Use Both Marijuana & Tobacco

Using both tobacco and marijuana is tied to significantly higher odds for depression and anxiety, a new study suggests.

Among nearly 54,000 U.S. adults, those who used both substances experienced anxiety or depression at nearly twice the rate of nonusers, researchers found.

"Smoking weed and tobacco does not help to deal with anxiety and depression, and may exacerbate mental health issues in the long run," said lead researcher Nhung Nguyen, an assistant professor of medicine at the University of California, San Francisco.

More research addressing the use of tobacco and cannabis is needed to understand effective prevention and treatment efforts for this "emerging public health issue," Nguyen added.

Co-use of marijuana and tobacco is increasing nationwide as more states legalize cannabis, the researchers noted, suggesting this could set the stage for mental health issues.

"Coordinating tobacco and cannabis cessation with mental health treatment may be beneficial for people with co-use of tobacco and cannabis," Nguyen said. "In addition, screening for use of tobacco and cannabis should be implemented in mental health treatment settings."

Why the combination of tobacco and marijuana might cause depression and anxiety isn't clear.

"The interaction between tobacco and cannabis on health in general and on mental health in particular is not fully understood," Nguyen said.

Moreover, this study can't prove that the combination of tobacco and pot causes depression and anxiety, only that a correlation may exist between the two, the researchers caution.

Nguyen acknowledged that people who are prone to depression and anxiety might be drawn to tobacco and cannabis as a way to feel better.

"Current evidence supports both directions of the relationship between tobacco and cannabis use and depression and anxiety," she said. "Evidence shows that use of either tobacco or cannabis contributes to anxiety/depression."

Past research also shows that people who are chronically anxious or depressed may be drawn to weed and tobacco.

For the study, Nguyen and her colleagues collected data on 53,843 adults who participated in online surveys as part of the COVID-19 Citizen Science Study from 2020 to 2022.

Asked about past-month substance use, 4.9% said they used only tobacco, 6.9% said they used only cannabis and 1.6% said they used both.

Among those who used both tobacco and cannabis, 26.5% reported anxiety and 28.3% depression. Among those who did not use either drug, 10.6% reported anxiety and 11.2% reported depression, the researchers found.

The odds of having these mental health problems were roughly 80% greater for those who used both tobacco and cannabis, compared with those who used neither, the study found.

Compared to folks who used tobacco only, folks who used marijuana (both co-use and marijuana only) had a higher likelihood of anxiety, but not depression, the researchers noted.

One expert not involved with the study believes it's more likely that people who are depressed or suffer from anxiety will self-medicate with tobacco or cannabis, not that that these drugs cause these conditions.

"The Achilles heel of this entire type of study is that correlation is not causation," said Dr. Peter Grinspoon, a primary care physician and cannabis specialist at Massachusetts General Hospital and Harvard Medical School.

"It's always made much more sense to me that people are just self-medicating and self-treating their anxiety and their depression," he said. "I treat a lot of people who treat their anxiety and depression with cannabis and it's very successful."

As for tobacco, "I generally think tobacco doesn't make anything better," Grinspoon said. "But we also don't know if it makes your depression and your anxiety worse."

He cautioned, however, that too much cannabis can be harmful and result in paranoia or other mental problems.

Grinspoon also noted that the link between depression and anxiety among those who used tobacco and pot in the study was worse among the poorest participants.

It's possible that poorer people have less access to mental health care and thus are less likely to be prescribed antidepressants or anti-anxiety medications, he said.

"If you're miserable by circumstances, who wouldn't be tempted to smoke or use cannabis?" Grinspoon pointed out. "In a perfect world, we'd all do yoga and eat tofu and meditate. But a lot of people have these really challenging lives and they're using these substances just to get by."

The report was published online Sept. 13 in the journal PLOS ONE.

More information

The Alcohol and Drug Foundation has more on cannabis use.

SOURCES: Nhung Nguyen, PhD, assistant professor, medicine, University of California, San Francisco; Peter Grinspoon, MD, primary care physician and cannabis specialist, Massachusetts General Hospital and Harvard Medical School, Boston; PLOS ONE, Sept. 13, 2023, online