Anti-depressants, or increasing a dose of an already on-board anti-depressant, has been shown to help people stop smoking. If this works, it implies that there is a neurotransmitter imbalance. I would address this differently than with pharmaceuticals, that's just my approach.
Biggest hurdle he has to face is that once he quits, it is forever. He will always have a yearning for it, he will have to deal with it, just like almost everyone else who quits anything.
The way I look at it:
First 3 days off are breaking the chemical addiction. This is the hardest.
First 3 weeks off are breaking the habits & patterns, actively making the choice not to smoke when the thought comes into one's head.
After 3 weeks off, if someone goes back to smoking, it is by their own choice.
I use laser acupuncture and a combination homeopathic remedy to help people stop smoking...it works pretty darn well. That said, if someone isn't or wasn't ready to stop smoking, nothing can help them. People can quit anything cold turkey once they are truly ready to make the choice.