Ellie, this man has been smoking grass since he was twelve. Few addicts stick to one drug. When Matt uses, Matt uses everything from acid to booze. He has been a using substances for nearly four decades now and he looks it. For the last three years he has been going hog wild living with someone who loves coke.
And, I disagree pot can't kill you. It's a progressive disease and he is hitting the end. Grass can be more insidious because you have this false confidence that's it's not as bad as other drugs. You can still function... Get to work, do your job, etc... But, in Matt's case, he has been smoking morning, noon and night... Literally, for decades.
He wakes up, gets high... Smokes to get through the day at work with one hitters... Goes big once home from work with some booze and grass, then smokes before bed to sleep. Everyday.
God knows what he mixes with the pot. Even if it's just booze, it will eventually bring you to the point he is at now. He looks like he has cancer.
"You know, it's times like these when I realize what a superhero I am." Tony Stark/Iron Man
“Focus on what you can do, then do it with all your heart.” Lois Wilson