New research suggests that cannabis use might alter the heart structure of the left ventricle. However, as the lead author acknowledges, the causes of the associations the team observed are unclear.

Researchers interviewed 3,407 participants and assessed their heart scans for the study. There were three groups of volunteers, all self-identified.

First were the 3,255 people in the “rarely/never” group, who used cannabis never or less than once a month. Second were the 105 people in the “previous” category, who reported regular daily or weekly use five years before the interview or longer.

Finally, the 47 “current” users reported regular, daily, or weekly use of cannabis within the past five years.

The average age of all participants was 62, and compared to both the “rarely/never” and “previous” groups, “current” users were more likely to be male, younger, tobacco smokers, and “socially deprived.” There was no discussion of what this might mean, but the connection between poverty and disease is well-understood.

Compared to “rarely/never” users, the team found that regular cannabis users were more likely to have a changed heart structure–specifically, a larger left ventricle. This is the main chamber the heart uses for pumping. They were also more likely to show early signs of impaired heart function.

The team found no differences between the groups for the size and function of the other three chambers of the heart. They also found no differences between the groups in the amount of blood pumped with each heart beat, or the total left ventricle mass.

Interpret heart structure study results carefully

The study’s authors were careful in their recommendations.

“Findings should be interpreted with caution, and further research is required to understand the potential pathophysiology, dose-response effects of cannabis use, and long-term implications of regular use on the cardiovascular system,” wrote the authors in the study. “Health care professionals and policy makers may need to advise caution on regular recreational cannabis use until such systematic research is available.”

Lead author Dr. Mohammed Khanji also told Newsweek: “It is unclear whether the associations observed are due to cannabis use alone or other unmeasured confounding factors.”

What comes next in the field? Hopefully, studies with larger numbers of diverse groups of participants that don’t rely solely on self-reporting. This would be particularly useful if it happened in a jurisdiction where cannabis was not illegal, so participants would not be lawbreakers.

These conditions would make for more reliable results and better information for everyone. There are many potential causes and confounding factors that could influence heart structure, so let’s not blame cannabis without solid evidence.