I believe that MDMA (aka Ecstasy) is another drug made illegal mostly because lots of middle-class people were enjoying it, not because it posed serious health threats. A PBS documentary on the history of MDMA I saw a couple of years ago pointed out that it was being used with some success by psychologists treating patients with intimacy issues. From Wikipedia: :
In the 1970s MDMA began to be used illicitly, and got the nickname “Ecstasy,” but while it was still legal and being produced commercially, there were apparently few if any reports of serious health problems. As I recall, the PBS show suggested that the decision to make it illegal was a political one, based on the drug’s popularity and not on any known health hazards. From the same Wiki article:
Ironically, the health problems became more common after it was made illegal, in part because the quality of the illegally produced drug was much lower on average. Also, the rare, but widely reported, deaths were mostly a result of people becoming seriously dehydrated while dancing at raves, and not as a direct result of the drug itself.
Furthermore, now that it is on Schedule I, it is politically difficult for scientists to make a case for conducting serious research on its clinical applications. Despite this, it is being studied for possible use in treating post-traumatic stress disorder.
There is a strong streak of prudishness among American lawmakers (and not a little cowardice) when it comes to drug laws. As Mr. Mencken said, Puritanism is the haunting fear that someone, somewhere, may be happy.