The issue of Judaisms view of drugs has been discussed numerous times.
I have said I support the medical use of Cannabis. I said this because I know that it works as a medicine. I also am against some of the drugs which the pharma companies are pushing on people. I say this because I have had to take some of those drugs and know that they are not good in the long term. This too has been discussed here many times.
Basically Tag Mahir is correct that Judaism is against things which are harmful to the body. It has been argued that a lot of things are harmful in a small way and yet it is permitted. So there must be a measure of how much damage is done. For instance, to this day, wine is a major part of Jewish rituals and yet wine has been shown to have negative aspects regarding health. While there are also reports that occasional use of wine is good for the health. This is the nature of science in todays world. There are scientific studies which contradict each other. Which ones do we believe?
I could list all the proclamations which scientists have made in my life which have changed back and forth, concerning colesterol, concerning global cooling vs global heating, concerning smoking good for alzheimers, etc. , etc. I take the scientists with a grain of salt till the studies start to show some reproducability {which is the scientific method anyway}.
I have seen a variety of studies recently and they do not conclusively point to danger in casual usage. Its use as a pain killer and other medical properties causes me to remain supporting its medical usage. We will see where this research goes..