do you think people who believe in god have a underlying mental illness or symptom?

[Angrboda]

I don't think that religion is inherently linked with mental illness, but I do think some mental illnesses can lead to religion. I'm undecided about those who speak in tongues, etc. Is "crazy" the same as "mentally ill"? People who say that god told them to kill some guy who was possessed by Satan are definitely mental, though.

I think the speaking in tongues and snake handling people are well within the range of normal. Humans are highly suggestible, and will do many remarkable things under the power of suggestion. Watch the performance of a good mentalist like Derren Brown and you'll see perfectly ordinary people induced to do things they wouldn't normally do. Note that even the speaking in tongues people don't evidence abnormal behaviors outside the context of the suggestion of their religion. Pentecostals don't take up flossing their sinuses like Hindu yogis, and Hindu yogis don't take up speaking in tongues. It's all couched within the norms provided within a cultural group, in imitation of the behavior of others. That's suggestion, not craziness.