Researchers who surveyed drug users in the U.K. found a high level of awareness about the harms associated with use of various substances, Medical News Today reported Nov. 26.

Asked to rank 20 drugs based on their harms, 1,500 drug users placed heroin, crack and cocaine as the top three most dangerous drugs; alcohol was ranked fifth, and tobacco ninth. Marijuana was ranked 18th.

The survey was conducted by University College London (UCL) and Imperial College London researchers. The ranking scale used in the study was based on a framework proposed by David Nutt, until recently the British government’s top advisor on drug issues.

“Given that the (U.K.’s) Misuse of Drugs Act aims to signal to young people the harmfulness of drugs, this suggests a flaw with the current classification of drugs. We found that drug users rated legal substances such as alcohol and tobacco as more harmful than Class A substances like LSD and ecstasy,” said UCL researcher Celia Morgan, who added that the study found “a high correlation between harm ratings by users and those made previously by scientific experts across all substances, suggesting users are well informed about the harms of drugs.”

Researchers also queried drug users on the perceived benefits of the drugs they took; LSD, marijuana and ecstasy were ranked highest in terms of their short- and long-term benefits by users. “We recommend that future health campaigns consider whether to include the benefits of some drugs,” said Morgan. “By only citing harms, such campaigns likely represent — from a user’s perspective — an unbalanced view and may mean that the overall message is more likely to be ignored.”

The 20 substances in the study were alcohol, alkyl nitrates, amphetamines, anabolic steroids, barbiturates, benzodiazepines, buprenorphine, marijuana, cocaine, crack, ecstasy, GHB, heroin, LSD, ketamine, khat, 4-MTA, methylphenidate, solvents, street methadone, and tobacco.

The research was published in the November 2009 issue of the Journal of Psychopharmacology.