A new study published in Nature Mental Health found that people who use both cannabis and tobacco may face a higher risk of developing serious mental health conditions such as schizophrenia, especially if they are already considered at risk for psychosis.
Researchers from Vanderbilt Health studied more than 1,000 participants in the North American Prodrome Longitudinal Study, focusing on people who show early or mild signs of psychosis but have not yet developed a full psychotic disorder.
The researchers tracked participants over two years and grouped them based on substance use: tobacco only, cannabis only, both cannabis and tobacco, other substances, or no substance use.
The study found that regular use of either cannabis or tobacco was linked to anxiety, depression, and early psychotic symptoms. However, people using both substances together did not show worse short-term symptoms compared to people using only one substance.
However, the biggest concern appeared over time. People who used cannabis heavily and tobacco occasionally were nearly three times more likely to develop psychosis than people who did not use either substance.
The researchers also noted that tobacco use is especially harmful for people with psychosis, as it is linked to major health problems such as heart disease, stroke, and lung cancer, and may reduce life expectancy by about 20 years.
The team said the findings are important for both doctors and patients. Reducing or stopping cannabis and tobacco use could help improve mental health symptoms and may lower the risk of developing psychosis in the future.
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