Effects can get more sedative the longer you leave it, but a sativa plant is not going to give the same effect as an indica just because you left it to ripen.
The key word is MORE sedative, more sedative than it would have been, does not mean couch lock.
The genetics determine the effect, the timing can just make it lean slightly one way or another.
As far as harvesting I agree with the other answers, you can harvest now, but I would wait a few days. Maybe a week.