People dream for a reason and one of those reasons could possibly be to relieve ourselves from daily reality things/issues/stress. Kinda like our mind is recycling our thoughts. Keeping it healthy and in-checked. When you LD, your changing your natural dreaming habits.

I don't know for certain if LD is the cause or the smoking/drinking, but I have to agree that when I started LDing again, I lost my appetite and felt more worried about things lately. I'm a non-smoker and I only drink on holidays...but I don't think it's something serious to worry about.