Is it time to consider cannabis smoking a cardiovascular risk factor?

Cannabis sativa is a plant believed to be native of ancient Scythia. For thousands of years, it has been used in several preparations as a psychogenic agent, and, in some cultures, as a medicine. In the middle of the 20th century, its use was demonized, but, more recently, a growing public debate about its effects has risen in many countries, as more permissive legislations have begun to be developed, both for medical and for recreational purposes [1]. Different preparations of C. sativa (commonly marijuana and hashish) are widely used, mainly for their euphoric effects, and cannabis is by far the most commonly used recreational drug in Europe, after alcohol assumption [2]. Recently, in the 2008 Annual Italian Parliament Report on Drug Addiction, it has been estimated that about 31% of the adult population (aged from 15 to 64 years), which is about 20 million people, have tried cannabis at least once in their life, with 7% of them using it at least once a month and 1.4% daily [3]. Moreover, as demonstrated by a recent US Government Report [4], marijuana is much more powerful today than it was 30 years ago and so are its biological effects. A recent report of Mississippi University showed that in the USA, average D-9 tetrahydrocannabinol (THC) levels rose from less than 1% in the mid-70s to more than 6% in 2002 [5]. Users and the public believe that marijuana and hashish are safe, although marijuana is far from harmless, being a contributing factor in more than 110 000 emergency department visits in the USA in 2001 [6]. Marijuana smoke contains from 50 to 70% more carcinogenic hydrocarbons than tobacco smoke and it may promote the development of respiratory tract cancer and impair immune system function [7,8]. Marijuana users have more suicidal thoughts and are four-fold more likely to report symptoms of depression compared with people who have never used the drug; moreover, cannabis use is associated with an increased risk of developing schizophrenia [9,10].