Now, this chart isn't a perfect comparison across the board. One driver of tobacco and alcohol deaths is that both substances are legal and easily available. Other substances would likely be far deadlier if they were as available as tobacco and alcohol. And federal data excludes some deaths, such as drugged driving deaths, which is why the chart focuses on direct health complications for all drugs.
Deaths also aren't the only way to compare drugs' harms. Some drugs, such as alcohol and cocaine, may induce dangerous behavior that makes someone more predisposed to violence or crime. Other drugs, like psychedelics, may trigger underlying mental health problems or psychotic episodes. When evaluating the overall harm caused by drugs, all of these factors should be taken into account. [...]
When it comes to deadliness, no single substance comes close to tobacco. To put its risk in perspective, more Americans die from tobacco-caused health problems like lung cancer and heart disease than from reported drug overdoses, traffic accidents, and homicides combined. [...]
The death toll may understate the more general risk of alcohol. A previous analysis, led by British researcher David Nutt and published in The Lancet, took a comprehensive look at 20 of the world's most popular drugs and the risks they pose in the UK. A conference of drug experts measured all the factors involved — mortality, other physical damage, chance of developing dependence, impairment of mental function, effect on crime, and so on — and assigned each drug a score. They concluded alcohol is by far the most dangerous drug to society as a whole. [...]
Marijuana is more widely used, but it's never been definitively linked to direct deaths or even other medical conditions. The research suggests using marijuana during adolescence could lead to some bad outcomes, particularly worse cognitive function. But studies have failed to conclusively link marijuana to lung disease or psychosis and schizophrenia, despite concerns from critics.