Researchers reported in the International Journal of Cardiology, "Marijuana use by older people, particularly those with some degree of coronary artery or cerebrovascular disease, poses greater risks due to the resulting increase in catecholamines, cardiac workload, and carboxyhemoglobin levels, and concurrent episodes of profound postural hypotension. Indeed, marijuana may be a much more common cause of myocardial infarction than is generally recognized. In day-to-day practice, a history of marijuana use is often not sought by many practitioners, and even when sought, the patients response is not always truthful".A 2013 analysis of 3,886 myocardial infarction survivors over an 18-year period showed "no statistically significant association between marijuana use and mortality".A 2008 study by the National Institutes of Health Biomedical Research Centre in Baltimore found that heavy, chronic smoking of marijuana (138 joints per week) changed blood proteins associated with heart disease and stroke.A 2000 study by researchers at Bostons Beth Israel Deaconess Medical Center, Massachusetts General Hospital and Harvard School of Public Health found that a middle age persons risk of heart attack rises nearly fivefold in the first hour after smoking marijuana, "roughly the same risk seen within an hour of sexual activity".Cannabis arteritis is a very rare peripheral vascular disease similar to Buergers disease. There were about 50 confirmed cases from 1960 to 2008, all of which occurred in Europe. Combination with other drugs
A confounding factor in cannabis research is the prevalent usage of other recreational drugs, especially alcohol and nicotine.
Edible forms of cannabis often contain several hundred milligrams of THC per dose, much more than the 32mg of a typical cannabis cigarette
According to the Merck Index, the LD50 of THC (the dose which causes the death of 50% of individuals) is 1270 mg/kg for male rats and 730 mg/kg for female rats from oral consumption in sesame oil, and 42 mg/kg for rats from inhalation.It is important though to note that cannabinoids and other molecules present in cannabis can alter the metabolism of other drugs, especially due to competition for clearing metabolic pathways such as cytochromes CYP450, thus leading to drug toxicities by medications that the person consuming cannabis may be taking. Related to smoking
A 2007 study found that while tobacco and cannabis smoke are quite similar, cannabis smoke contained higher amounts of ammonia, hydrogen cyanide, and nitrogen oxides, but lower levels of carcinogenic polycyclic aromatic hydrocarbons (PAHs). This study found that directly inhaled cannabis smoke contained as much as 20 times as much ammonia and 5 times as much hydrogen cyanide as tobacco smoke and compared the properties of both mainstream and sidestream (smoke emitted from a smouldering joint or cone) smoke. Mainstream cannabis smoke was found to contain higher concentrations of selected polycyclic aromatic hydrocarbons (PAHs) than sidestream tobacco smoke. However, other studies have found much lower disparities in ammonia and hydrogen cyanide between cannabis and tobacco, and that some other constituents (such as polonium-210, lead, arsenic, nicotine, and tobacco-specific nitrosamines) are either lower or non-existent in cannabis smoke.