Possible causes of your friend's unfortunate disaster include:
1) It wasn't MDMA/MDA (typical Ecstasy components), as binarymax suggested. Until drugs are legal, who the hell knows what you're actually taking. Could be anything, including washing powder. Unlikely to be actually poisonous stuff, since dealers like repeat customers too, but really, it could be anything.
2) Your friend took an exceptional amount, was not used to intoxicating substances, and had very fragile kidneys. Perhaps his kidneys were about to give up anyway, and Ecstasy just pushed him over the edge. Maybe a good drunken night would have done the same thing.
3) It was just a coincidence.
I suspect a combination of 1 and 2... probably it wasn't Ecstasy, and your friend was already in danger of blowing his kidneys anyway.
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Some fun numbers from http://thedea.org/technicalFAQ.html:
>"MDMA-present" drug deaths occur at a rate of aproximately 2-3 users per 100,000 users/year. ... cigarettes ... on the order of 400 deaths per 100,000 users/year
With only "a handful" US-annually where it was the only drug, out of less than a hundred. Think alcohol can claim that?
Thankfully it isn't at all addictive so it's not hard to stop. :)
Either way, it falls solidly on the side favoring ecstasy over tobacco.
How would you define a "hit" anyway? Doses don't really compare, and even if it's 1-cigarette/1-pill, it's all societal how much is in each "dose"...
If you try to say, what is more dangerous - taking one ecstasy tab or one cigarette - even if the ecstasy is more dangerous in the short term, the possibility of addiction could make the cigarette much worse.
I guess maybe you could work the other way - start with say, 1 cigarette, and then try to calculate what amount of ecstasy is an equivalent dose? However I would guess that it fluctuates largely on how much you have at the same time?
I.E. One day you'll have rubbish "Roles Royces" and you'll have 6 of em, another you'll have some nice "Mitsis" and just take 3 and on other days you'll have an insane "Red Tulip" that was incredibly more potent than all the others so you only needed one. Of course the name never really means anything as you can have both good "mitsis" and bad "mitsis".
Then there is also the case where the pill is actually cut with something else (pretty common I believe), perhaps a bit of ketamine or god knows. The issue perhaps is that an "ecstasy" in its black market form may be very different from its medical definition making it very difficult to compare like for like.
(That's exactly the same problem actually - buying black-market alcohol. Which is still pretty big in Russia and neighbouring countries.)
Anyone with internet access should be able to sidestep this problem altogether. Manufacturing MDMA or Meth at least requires acquiring lab equipment and some fairly dangerous chemicals, plus some knowledge of chemistry, which is understandably above the abilities of some people. But any idiot can make booze.
That is probably a lot less drastic than the effects of e.g. getting completely drunk every day. But one of the problems is that there is no public evidence based knowledge about the effects of drugs like Marijuana. People either believe it's completely harmless, or they think it's the devil. There is also no good social canon on the use of such drugs. Getting drunk every day has obvious social stigma in all circles, but smoking hash every day can be accepted behaviour in certain circles.
That is actually the nice thing about this study, they try to correct this and give facts.
Citations, please.
A phrase to remember when citing anecdotes about mentally ill people taking Drug X is self-medication. This is a technical term in counseling psychology; it refers to a very common phenomenon where a person who is suffering a mental health issue -- which can be anything from a mild acute depression to full-blown schizophrenia -- figures out, by trial and error, that taking a certain drug seems to alleviate their symptoms, or make those symptoms more tolerable. This often causes the patient to end up with two health problems, which can be difficult to sort out from each other and which generally must be treated together.
So even if you uncover evidence that mental illness and taking drugs are correlated, you can't simply assume that the drugs cause the mental illness. It could just as easily be the other way around.
Some Googling finds this: Pope HG, Gruber AJ, Hudson JI, Huestis MA, Yurgelun-Todd D. Neuropsychological performance in long-term cannabis users. Arch Gen Psychiatry 58(10):909–915, 2001.
Your caveat about correlation and self-medication could be right. It might also be wrong - you don't give a good citation either. My point was that I think we have a lot less knowledge about the effects of these drugs than e.g. alcohol which we're (ab-)using since millenia, so the UK analysis is certainly an improvement.
the source is not very reliable(some obscure journal in portugese),
A very small percentage of people are smoking it for health effects. The rest just want to forget about whatever is going on in their lives and get high. Why can't people just admit the truth?
Many people consuming alcohol are doing so for similar reasons.
I'm just curious, your opposition seems largely centered on people being high and not the medical effects, are you a prohibitionist too? What about self-induced altered states of mind, hypnosis, etc? Neurochemically active foods (chocolate->dopamine link)? What's the reasoning?
What's interesting there is that a glass of wine a day (which might be healthy, though such claims get regularly debunked) is socially accepted. I think our societies just have better knowledge of acceptable use of drugs that we're more familiar with, as a whole.