People with psychoses link cannabis use to physical ills

People who have psychotic disorders, such as schizophrenia, and who also use cannabis report experiencing a wider range of health problems than previously documented. New research shows that individuals with these conditions reported not only worsening mental health symptoms, but also elevated rates of physical health problems, which they attributed to cannabis use. 

“From past research, we know that people with psychoses often use cannabis. Our paper suggests that this population faces disproportionate harms of deteriorating psychiatric and physical health,” said Beatriz Carlini, the study’s first author. She is a research associate professor of psychiatry and behavioral health sciences at the University of Washington School of Medicine.  

The findings were published Jan. 16 in Community Mental Health Journal. 

Carlini and colleagues analyzed responses from 4,144 Washington state cannabis users who were surveyed between 2020 and 2023. The survey was part of data gathered for the University of Waterloo's International Cannabis Policy Study, an ongoing project.  

Among cannabis users with psychotic disorders, 61.3% reported experiencing adverse health events in the previous year — compared with 38.1% of people with other mental health diagnoses and 23.0% of people without any mental health diagnosis. Among people with psychotic disorders, 28% had sought medical attention for cannabis-related problems in the same span, compared with only 8.1% and 3.8%, respectively, of members of the other groups. 

The authors noted higher reported rates of physical health symptoms in the study population: 

• Nausea and vomiting: 20.6% (vs. 9.4% and 5.5% in comparison groups) 
• Heart or blood pressure problems: 17.5% (vs. 5.4% and 2.0%) 
• Dizziness and fainting: 26.1% (vs. 9.8% and 5.3%) 
• Cannabis hyperemesis syndrome (severe, repeated vomiting): 26.8% (vs. 8.7% and 3.8%) 

Higher rates of mental health symptoms also were reported by the study population: 

• Hallucinations or psychotic episodes: 17.6% (vs. 3.2% and 2.8%) 
• Flashbacks: 12.1% (vs. 2.8% and 1.1%) 
• Panic reactions: 17.5% (vs. 5.4% and 2.0%) 

The researchers’ data came not from medical records or physician observations, but from cannabis users themselves, who related their medical histories and perceptions in an online survey. 

"This self-reported approach captures experiences that might never make it into a doctor's office, while also revealing how users themselves perceive the relationship between cannabis and their health problems,” Carlini said.  

The research team acknowledged the methodology’s main limitations: Patients may not always accurately identify what's causing their symptoms. The study’s design leaves unclear whether cannabis use causes other health problems or simply correlates with them.  

“But personal perspectives are important,” Carlini said. "To understand the puzzle of how cannabis adverse events are evolving, you need data from several sources.” The investigators are working to triangulate information from patient reports, physician observations and medical records, she added. 

People with psychoses who use cannabis likely increase demand for healthcare services beyond those associated with managing their psychiatric conditions alone, the authors wrote. Many individuals with psychoses may be unaware of their heightened vulnerability to cannabis-related harms. 

"We want mental health providers to better understand that addressing cannabis use among their patients who suffer from schizophrenia and other psychotic disorders is really important," Carlini said. "Paying attention to cannabis is in the best interest of this population." 

The researchers have developed a clinical guide to help practitioners have these conversations with patients. They also recommend public health campaigns and warning labels on cannabis products targeted at individuals with mental health diagnoses, particularly those with psychotic disorders.  

The research was funded by the Washington State Legislature through ESSB 5187 (2023), the University of Washington's Cannabis Dedicated Account, and the Canadian Institutes of Health Research. 

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