On one level, duh: pot relaxes you. I know, tempting to just leave it at that.
More interesting, however, is what this is an indication of. California legalized pot for medical purposes, and that actually made it possible to study marijuana and its effects in a Real Scientific = Randomized Double Blindy kinda way. Expect a _lot_ more studies like this to roll out over the next few years, rising in crescendo and actually getting interesting once the ones that started this last year (after the Feds said, f*ck it, we don't feel like arguing with you any more) are done and published.
The first few, however, will be painfully obvious.