Half a g of thc (so, lets say an edible made from 2g high quality weed)? or do you mean 0.5g weed or hash?
If the former well, that's one hell of a dose! 10% of that eaten would have me super stoned for 5 or 6 hours and I'm a lifetimer.
I don't think 500mg thc would make me anxious though - just abolutely beyond high, perhaps uncomfortably so dunno...the thought of it does not appeal at all and I truly loves me cannabis
I did once eat a whole 3.5g of just-purchased pretty good squidgy black hash in my early 30's once though (thanks very fucking much to the cops...pulled me over a few seconds after I drove off after scoring, was certain to be searched so I ate the lot, he just told me to get a break light fixed and sent me on my way. It wasn't decarbed so I thought it wouldnlt be much of an issue - wrong! Got home, laughed my ass off for an hour or 2 and then spent the next
24 hours or so in/out of sleep or hyper-drowsiness, unable to even speak as too much effort, had loads important stuff to do which I obvs could not do...the mrs was fukkin fuming, ahem. Makes me wonder if the whole decarbing thing is as important as believed - I was FUCKED lol