There is such a thing as addiction to marijuana. He may or may not have it, and it may or may not have something to do with his actions here, but it does exist.

Some people in the comments at that link are trying to make a distinction between "physically" and "psychologically" addictive. This is a common belief, but medically, there are no such distinctions. Addiction is defined as continued use despite consequences, and whatever the mechanism, it occurs with marijuana in some people.