"Method: Members of the Independent Scientific Committee on Drugs, including two invited specialists, met in a 1-day interactive workshop to score 20 drugs on 16 criteria: nine related to the harms that a drug produces in the individual and seven to the harms to others. Drugs were scored out of 100 points, and the criteria were weighted to indicate their relative importance."
"Findings: MCDA [multicriteria decision analysis] modelling showed that heroin, crack cocaine, and methamphetamine were the most harmful drugs to individuals (part scores 34, 37, and 32, respectively), whereas alcohol, heroin, and crack cocaine were the most harmful to others (46, 21, and 17, respectively). Overall, alcohol was the most harmful drug (overall harm score 72), with heroin (55) and crack cocaine (54) in second and third places."
Nutt, David J Nutt; King, Leslie A; Phillips, Lawrence D, "Drug harms in the UK: a multicriteria decision analysis," The Lancet (London, United Kingdom: November 1, 2010) Vol. 376, p. 1558.