It is my impression that religious belief has a lot of similarities with schizophrenia or other mental ailments. In particular, fanatical belief, as is demonstrated by this lovely piece of news. So, this idiot sees what he believes to be the mark of the devil in his hand, and proceeds to lop it off himself because the bible tells him so...
So let's analyse this shall we?
Wikipedia defines schizophrenia as follows:
Schizophrenia, from the Greek roots schizein (σχίζειν, "to split") and phrēn, phren- (φρήν, φρεν-, "mind"), is a psychiatric diagnosis that describes a mental illness characterized by impairments in the perception or expression of reality, most commonly manifesting as auditory hallucinations, paranoid or bizarre delusions or disorganized speech and thinking in the context of significant social or occupational dysfunction.
Now let us compare it with religious belief:
Auditory hallucinations: The most devout believers claim to hear their deity of choice.
Paranoid or bizarre delusions: Many believers claim they are under the watchful gaze of an all mighty but improbable god who will banish them to some fictitional hell if they do not behave according to some self contradicting book written millenia ago.
Therefore, their perception of reality is highly impaired. I wonder why that has not yet been classified as a mental illness...