As for the depression part they are also looking at it wrong. People who are depressed have a tendency to smoke. Not the other way around.
Correct. Smoking rates among those with schizophrenia are three times higher than among the general populace. I have yet to hear this used as evidence that tobacco causes schizophrenia.
Although it's also interesting why this should be. I mean, it's not like some non-smoker is going to think "I don't feel good due to my schizophrenia. Hey, I know, I'll start smoking!" I think what happens is that people with mental conditions, like most others in society, will experiment with smoking in their teens. For whatever reason, their brains latch onto the effects of nicotine much more readily and create dependence quickly.