We have a funky uhh... Circadian rhythm says the dictionary. Anyway, last summer when my friend and I grew out out first ever cannabis plants (NL auto and AKR) outdoors, they showed sex at five weeks or so.
Now, they were horribly stunted anyway. Despite that I do believe increasing the amount of light tells the plants to hold up with the hormones. I'd try it out now that I grow indoors, but my space is really limited.
EDIT: I too would be extremely happy to get to the bottom of this. I've thought about it often.