Years of meditation lead me to believe than the line between mind and body is not clear at all. E.G: every time you are angry, you clench some part of your body. Well, if you observe yourself when you feel depressed, or stressed, you'll notice your body is full of very unpleasant sensations. They are not illusions, your body is litterally reacting to your toughs all the time, in many subtle and diverse ways.

I now deeply believe (I'll admit I have no more evidence than my subjective experience) that many of our abusive substance intakes, be it cigarettes, alcohol, weed or even coffee or sugar, are in part to cope with those unpleasant physical sensations, not just the mental burden. Slowly, you build a physical intolerance to them because you are used to be liberated from them using whatever is substance you abuse.

And hence I do think there is a physical addiction as well.

E.G: if you can't cope with stress without getting some THC, I don't classify that as only mental, as stress is not a phenomenon that is only in the mind, but affect the entire nervous and hormonal system.