Here are some facts on the weed issue:
1.) The effects we feel from marijuana come, at least primarily, from molocules that have an affinity for anandamide receptors. We get that word from the sanskrit, ananda, meaning, "to give pleasure."
2.) The most common psychotropic substance in marijuana is delta-9 tetrahydracanabinol (THC).
3.) The effects of marijuana vary widely from person to person. With some people it acts like a sedative, in some a stimulant; it can even induce symptoms of acute paranoid schizophrenia in some poor souls.
4.) I know a good deal of high level athletes who smoke before work outs with good results (discerning if the results are, "good" by the quality of their work outs and the quality of their competition). Indeed, I know of several who compete and consistently win while under the influence of the herb. You can say up and down that it's the placebo effect, but there's a lot of data to suggest that, in some individuals, marijuana can actually increase concentration.
5.) A life time friend who's a Navy SEAL (team 3) informed me that many of the SEALs in his platoon smoke before nightime operations to increase sensoryperception and focus.
M'kay...