This author doesn’t seem to be aware that correlation does not equal causation.

He know the difference, that is the whole point of the study :

|However, researchers have not been able to agree on whether smoking causes depression or other mental disorders, **or **whether we smoke because we need to lessen the symptoms of a latent mental disorder. But now we know.|

Your experience though valid, is not a study about 350 000 people. And I'd rather believe the scientists (who spent their life interpreting data like that) when they say :

"Smoking typically comes before the mental illness. In fact, a long time before.