From the article: “Prof Nutt told the BBC: ‘Overall, alcohol is the most harmful drug because it’s so widely used.'” It has to be noted that any measure of harm that does not control for how widely a substance is used is a useless measure in debates over legalization. Of course, alcohol is more widely used because it’s legal, and the various illegal substances on the chart are less widely used precisely because they’re illegal. That tells nothing of the harm or lack of harm from these substances if they were legalized.