I'm not going to say that this is 100% definitive, because, what is in life? - but in general, Cannabis is simply not a harmful substance. You can consume as much as you want, with whatever you want, but that's not to say there aren't side effects. Edibles are "dangerous" if you will, for those who are not regular consumers because it is more difficult to titrate dose than with say, smoking a joint or a bowl, where one can take a small hit, a large hit, one hit, several hits and so on. With an edible, you won't feel effects for some time and could potentially consume too much.
This isn't a medically dangerous situation, but you can certainly have a full-on psychedelic trip from Cannabis overdose, which can be quite frightening if one is not prepared for it. I, and the medical community it would seem, encourage the use of Cannabis with Opioids to either reduce the amound of Opioids needed or to potentiate the current dosage. I can say for myself that Cannabis has a definite syngergy with most Opioids.