Alcohol is ranked almost as harmful as heroin in a controversial new drug classification system proposed by a team of British scientists.
Ecstasy, rated a Class A drug in Britain, is placed near the bottom of the league table which lists "harm scores" for different substances. LSD, another class A drug, is also considered relatively safe despite its powerful hallucinogenic properties.
Cannabis, recently downgraded by the British government to class C, occupies a middle position. It is rated more dangerous than Ecstasy, LSD and the dance floor drug GHB - but less harmful than tobacco.
The table, published in The Lancetmedical journal, was drawn up by a team of scientists led by Professor David Nutt, from the University of Bristol, and Prof Colin Blakemore, chief executive of the Medical Research Council.
It is intended to be a model for policymakers that is more scientifically based than the current Misuse of Drugs Act system that attaches "a, b, and c" labels to illicit drugs.
The results placed heroin at the head of the table with an overall "harm score" of 2.7, followed by cocaine which scored 2.3.
But more controversially, alcohol is ranked as the fifth most dangerous drug, scoring just under 2 on the table.
The scientists identified three main factors that together determined the harmfulness of a controlled substance.
These were: the physical harm to the individual user caused by the drug, the tendency of the drug to induce dependence, and the effect of the drug's use on families, communities and society.