The study isn't just looking at the individual impact, but the social impact as well. So once you've factored in the alcohol related violence, cost of alcohol on the NHS, impact on the individual etc, the study is saying it is the most damaging drug. Heroin and crack cocaine both have a huge social impact as well, so they score high.
This is anecdotal but when I did my doorman course a few years ago the police explained that thewwre are, generally two ways a heroin adict can fund their habit; prostitution and theft. If they are stealing and shoplifting they will only get 10% to 20% of the value of the goods. So if they have a £50 a day habit then they will be stealing, potentially, £500 worth of stuff a day. So only a couple of addicts in an area can have a huge impact on the crime rate.
Whereas ecstasy has an individual impact, but the social in term of crime and violence is low, and mushrooms causes the occasional tresspass of a farmer's field.
No view either way on the validity of the study, but I can see how the figures have been arrived at.
For those interested in drugs, as it were... the infamous David Nutt (partly responsible for the data in that graph, fired from UKgov advisory committee & amusingly, my-wife-the-shaman's supervisor when she got her neurochem Masters) blogs here & tweets as @ProfDavidNutt
These were recorded while Brooker was still working for PC Zone and were featured on, I believe, the 100th issue cover disk. I highly recommend the BMG one.
Madonna's infamous 1994 interview with David Letterman. My favourite part is where she pulls out a pair of her undies and tries to get Dave to smell them.