What does "mental" mean in this sentence?
He said no, he didn't remember that at all, and she signed deeply to let him know she thought he did, pointing, then, to a house on the corner done all in blue lights, strings of blue lights up and down the whole front of it, turning her head to keep looking as the car moved past.
He said, "I am mental, Janie."
"Very mental," she agreed. "You have the ticket?"
He nodded.
"Funny to have tickets in order to get into a church"
..........

Could anyone tell me what "mental" means in the conversation?

Question

What does "mental" mean in this sentence?
He said no, he didn't remember that at all, and she signed deeply to let him know she thought he did, pointing, then, to a house on the corner done all in blue lights, strings of blue lights up and down the whole front of it, turning her head to keep looking as the car moved past.
He said, "I am mental, Janie."
"Very mental," she agreed. "You have the ticket?" 
He nodded.
"Funny to have tickets in order to get into a church"
..........

Could anyone tell me what "mental" means in the conversation?

Answer

It means that someone is behaving so erratically that they can be considered to be mentally sick, in a clinical way. So it is a form of exaggeration, to make a point. “I’m mental” is a shortened way of saying “I’m mentally retarded”. “Mentally retarded” is not considered polite these days; “mental” is less offensive. This slang is not so prevalent in the US but I think I hear it more in British media.

Answer

It is a British-English way of saying “mentally ill” (insane).  We don’t use “mental” this way very much in the United States.

Answer

Using mental in British English is not always literal, but a way of saying that you’ve done something crazy or stupid.

Answer

Thanks guys for your comments. No, he doesn't have amnesia. Though he is old, he is very healthy and even cheats on his wife (without her noticing). I think as Stanley Ng said, it's an exaggerating way used for him to explain why he didn't remember small things about his wife on their early married days (is it correct to say "on their early married days"?).

Answer

mental这个用法挺有意思，好像汉语里说，这人有点神经。