Regular cannabis use could affect heart structure and function, new research suggests.
Experts found an association between regular use of the drug and an enlarged left ventricle – the main pumping chamber of the organ – together with early signs of impairment of heart function.
The team, led by Queen Mary University of London, identified the link using MRI images from the UK Biobank population study.
Lead author Dr Mohammed Khanji, senior clinical lecturer at Queen Mary, said: “Our findings are not conclusive but the research took place against a backdrop of decriminalisation and legalisation of recreational cannabis use in many countries.
“We urgently need systematic research to identify the long-term implications of regular consumption of cannabis on the heart and blood vessels.
“This would allow health professionals and policymakers to improve advice to patients and the wider public.”
Cardiac scans for 3,407 individuals were analysed.
They had an average age of 62 and did not have cardiovascular disease.
Most of them – 3,255 – rarely or never used cannabis, 105 had used it regularly but more than five years before they were interviewed, and 47 were current regular users.
Researchers found that the latter group were more likely to have larger left ventricles and show early signs of impaired heart function, measured by how the heart muscle fibres deform during contraction.
However, according to the study, there appeared to be no difference between the three groups in the overall mass of the left ventricle or the amount of blood ejected with each heartbeat.
No changes were identified in the size and function of the other three chambers of the heart.
The analysis also found that people who had used cannabis regularly but given up had similar heart size and function to those who had rarely or never taken the drug.
Scientists acknowledged limitations of the study included the over-representation of white participants (96%), the relatively low number of regular cannabis users, the reliance on self-reporting a drug that remains illegal in the UK, and the possible impact of unmeasured confounding factors.
Dr Khanji added: “We believe this is the first study to systematically report changes in heart structure and function associated with recreational cannabis using cardiac MRI, which is a very sensitive imaging tool and the current reference standard for assessing cardiac chambers.
“The World Health Organisation has warned about the potential harmful health effects of non-medical cannabis use and called for more research specifically around the cardiac impact.”