What abused drug do you think is the most harmful? Do you think it's , a drug that can cause a rush of pleasurable sensations and has strong addictive properties? Do you think it's crack , a drug that is associated with powerful feelings of well being and high energy and is also highly addictive? How about LSD or mushrooms, that cause strange and mystical experiences?

You may be surprised to learn the results of a major study conducted by David Nutt and colleagues in the UK and recently published in the journal Lancet. The most harmful drug is ... . How is "harmful" characterized? In this study, harmfulness was divided into two major categories: harm to the user and harm to others. Each of these groups was further divided into subcategories, leading to a total of 16 subcategories of harm. Each subcategory was "weighted" in such a manner that a harmfulness score of 60 indicates that a drug is about twice as harmful as a drug with a score of 30.

When the investigators examined total harmfulness scores, the big winner (or should we say the big loser) was alcohol. Alcohol had a score of 72 (out of a possible score of 100). Heroin came in a distant second with a score of 55, with crack cocaine close behind with a score of 54.

As already mentioned, the total harmfulness score takes into account both harm to self and harm to others. Is alcohol still the most harmful drug if only harm to self is considered? No. When only harmfulness to the individual (and not to others) is examined, heroin, crack cocaine, and lead the pack with subscores around 35 versus alcohol's harm to self subscore of 27.

We all know that are extremely addictive and costly in terms of causing multiple serious medical conditions. Its total harmfulness score was 26. This is somewhat counterintuitive to us since cigarette leads to heart disease and cancer. When taking these smoking-related illnesses into account, cigarette smoking is the leading cause of death in the US (accounting for more than 400,000 deaths per year). However, when all 16 subcategories in the total harmfulness score were included, cigarettes were considered less harmful than alcohol. The fact that alcohol leads to injuries and deaths from violence and traffic accidents, while tobacco is quite low in this subcategory, contributes significantly to the differences in ranking.

What about cannabis ( )? It was rated as being less than one-fourth as harmful as alcohol with an overall score of 20. Although this is probably correct from a societal standpoint, increasing data suggest that early cannabis use is a risk factor for serious disorders and perhaps the use of more problematic drugs of abuse. What about hallucinogens such as LSD and mushrooms? These drugs had total harmfulness scores around 6 to 7, and ecstasy was rated at a 9.

What do these results mean? Does this study suggest that drugs like LSD, ecstasy, and mushrooms are safe, and, therefore, we should ease restrictions on their use or availability? This is clearly not the intent or recommendation of this study. Humans, especially younger individuals, have a strong tendency to experiment with drugs. Easing restrictions may lead to substantial increase in use. Among the factors contributing to the relatively low harm attributed to hallucinogens is their low overall use in the population. It is also important to remember that it is relatively rare for individuals to abuse a single drug. For example, nicotine dependence is extremely high among alcoholics, and polysubstance use and experimentation is more the norm than the exception.

Even though this study emphasizes that alcohol can be extremely harmful, it does not mean that alcohol is harmful to all who enjoy a drink or two. In fact, there are data suggesting that limited alcohol consumption may have health and social benefits. The issue with alcohol is that a significant percent of drinkers, perhaps about 25%, have trouble controlling their use of alcohol. This 25% includes some who abuse alcohol, others who become addicted to alcohol, and still others who drink heavily and have medical consequences from such drinking.

From a public health perspective, recreational , including abuse of legal drugs such as alcohol and cigarettes as well as illegal substances like heroin, cocaine, and methamphetamine, wreaks havoc on society with medical, financial, and social consequences. It will not be easy to figure out how to minimize the harm done by these agents. Research that helps us better understand the nature and extent of the problems is a useful first step.



This column was co-written by Eugene Rubin MD, PhD and Charles Zorumski MD.