A University of Bern analysis of data from a 25-year study showed that smoking marijuana was only associated with clogged arteries in lifetime tobacco users.
Scientists have long known that smoking tobacco is associated with atherosclerosisexternal link – a condition in which arteries are clogged by the build-up of fatty deposits called plaques – especially in arteries that supply blood to the heart. But there has been scientific disagreement over the effects of marijuana.
Reto Auer at the University of Bern Institute for Primary Health Care led an international team of researchers in analysing data on 3,498 men and women who participated in the 25-year US‐based Coronary Artery Risk Development in Young Adults (CARDIA) study.
"We knew the effect of tobacco smoke, but not of marijuana smoke on subclinical plaque build-up in heart arteries (a marker of future heart attacks). We sought to determine the association between lifetime exposure to marijuana and measures of plaque build-up in mid-life," said Auer in a University of Bern press releaseexternal link.
As expected, the scientists found a strong link between tobacco exposure and the appearance of plaques in coronary arteries in the abdomen. However, among middle-aged cannabis smokers who had never consumed tobacco, such a link could not be identified.
According to the study authors, frequent consumption of cannabis only has a weak influence on atherosclerosis risk. However, they added that when tobacco and cannabis are smoked together, the negative health effects should not be underestimated.
"Our study confirms the strong and consistent association between tobacco use and plaques build-up. The broader public health implications of high prevalence of tobacco use among marijuana users is alarming," added co-author Stephen Sidney, a principal investigator of the CARDIA study.
The results have been published in the journal Addictionexternal link.