what is the source for that chart, and how did they operationalize physical harm, social harm, etc?
there's some stuff that is being hidden by the way they categorized the drugs. for example, they presumably collapsed crack and cocaine into one category (they have the same active ingredient), but crack ends up causing a lot more social harm and has a higher risk of dependence than cocaine HCl (assuming the cocaine is not smoked or injected but possibly even then). this harm is mitigated by averaging that social harm/risk of dependence with the social harm/risk of dependence of sporadic cocaine use among the millions of college kids and yuppies.
likewise, i'm assuming methamphetamine falls under the amphetamine category, but that leads to a drastic understatement of its risk as well. methamphetamine causes pretty severe damage to the dopamine system, and its risk of dependence and negative social consequences are well known. however, when you average those with the much-less-extreme risks/effects of high school/college kids, soccer moms, professionals, etc abusing amphetamine (ie, adderall), the fact that methamphetamine is a very harmful drug is not properly represented.
when i was talking about 'worst' drug, i was referring to the worst drug pharmacologically (ie, what causes the most physical damage when administered regularly in its pure form), essentially, what is the worst drug in a social vaccuum? (i used to study pharmacology) ultimately, the effects of the drug in its social context are what matters for making policy, etc, of course.
it's just that when people who binge drink regularly are, like, 'OH NOEZ it's teh heroin!!!!!!!' it is potentially a little hypocritical. i would argue that binge drinking over time is harder on the body than using opiates, possibly heroin, regularly over time. that argument could certainly be contended, but my point is that damage from alcohol and damage from heroin are not as different as people assume.