[gwern]

I think negative ones aren't even worth including and would confuse it. Also, when they prove really negative like ephedra, don't they usually get banned?

[zck]

I was thinking more along the lines of "we tested this, and it doesn't help condition X", not "this will harm you". The article's down now, but I recall the lowest level being "no evidence". That implies that no tests have been done.

[somecanuck]

Ephdra is not banned in the US, it's merely restricted. It's still available over the counter in Canada as well.

[sp332]

It's definitely banned in the US. There are some "safe ephedra" products which are actually some other stimulant - usually bitter orange.