I can't speak for the other posters but wanted to clarify that this is not what I said or meant to imply.

I merely meant to mention the side issue that there are other aspects/effects to consider than the purely physical. Heavy users (by which I mean those who smoke habitually throughout the day - as opposed to recreational users), do, from my observations, experience changes in their life such as impaired social skills.

As one person mentioned, it is definitely not something for everyone, and not advisable in the USA where employers are allowed to (and do) spot check their employees for drug use whenever they like. But use of marijuana is pretty harmless, when used in moderation (i.e. recreationally). And, some people can and do take it heavily/habitually without any negative consequences too. As for those physical effects, it's long been my opinion that the safest way to consume it is to cook with it and and eat it.