Nov. 1, 2010 -- Alcohol abuse is more harmful than crack or heroin abuse, according to a new study by a former British government drug advisor and other experts.

Neuropharmacologist David Nutt, MD, of Imperial College London, and colleagues rated 20 different drugs on a scale that takes into account the various harms caused by a drug. Drugs are rated on nine harms a drug causes an individual and seven harms a drug causes society.

The scale, developed by a panel of experts called the Independent Scientific Committee on Drugs (ICSD), ranges from 0 (no harm) to 100 (greatest possible harm). It is weighted so that a drug that scores 50 is half as harmful as a drug that scores 100.

"The highest and lowest overall harm scores … are 72 for alcohol and 5 for mushrooms," Nutt and colleagues calculate. "The ICSD scores lend support to the widely accepted view that alcohol is an extremely harmful drug both to users and to society."

Alcohol was found to be the most harmful drug to society and the fourth most harmful drug to users.

The findings should come as no surprise: Alcohol has been linked to more than 60 diseases.

"Alcohol does all kinds of things in the body, and we're not fully aware of all its effects," alcohol researcher James C. Garbutt, MD, of the University of North Carolina at Chapel Hill, recently told WebMD. "It's a pretty complicated little molecule."