They used to say that about cigarettes too. I don't think marijuana is anywhere near as addictive as tobacco, but clearly there are people who have a great deal of difficulty quitting marijuana, who will use it habitually when they know using it is causing them problems. Maybe it's just like Internet addiction or gambling addiction. I don't know. I tend to think though that even psychological addictions are actually physical. What goes on in your brain is not magic. It's all electrical, or chemical neurobiological function, something physical. I think there is probably less difference in what we term “physical addiction” and what we call “psychological addiction” than we think.
Thank you for the well thought out response. It’s rare on these threads this day and age.