Individual harm (such as dependence, mortality, and impairment of mental functioning) was considered under "harm to users," while "harm to others" (such as crime, environmental damage, and international damage) took into account the number and extent of others harmed by individual drug use.
The two charts below illustrate the study’s conclusions using a 100 point scale where 100 is the maximum harm and zero indicates no harm. The first chart broadly illustrates all 20 drugs by "harm to users” and harm to others” while the second chart illustrates those drugs on 16 criteria from drug-specific mortality to dependence to family adversities.
The study concluded that alcohol was the most harmful drug overall (72 out of 100), followed by heroin (55 out of 100), and crack cocaine (54 out of 100). The most harmful drugs to users were crack cocaine, heroin, and methamphetamine (scores 37, 34, and 32, respectively), whereas alcohol, heroin, and crack cocaine were the most harmful to others (46, 21, and 17, respectively). Cannabis (aka marijuana) had an overall harm score of 20, putting it in eighth place behind amphetamine (aka speed) and before GHB (aka liquid ecstasy).
Last updated 4 January, 2012 
