I've read (mostly things by Ron Maimon) that marijuana* can actually impair your ability to do calculations (and in extent, I'd also assume your ability to make decisions) and I'm curious if there's any truth to that.
There are long-term effects, but the impact seems to be not fully clear (wikipedia, On the other hand there are many known side-effects of the normal drugs used for the same purpose.
Beside the medical properties there are also the social properties of a drug.
See also the AMS report Brain science, addiction and drugs.
If it's worth saying, but not worth its own post (even in Discussion), then it goes here.
Notes for future OT posters:
1. Please add the 'open_thread' tag.
2. Check if there is an active Open Thread before posting a new one. (Immediately before; refresh the list-of-threads page before posting.)
3. Open Threads should be posted in Discussion, and not Main.
4. Open Threads should start on Monday, and end on Sunday.