Hello! Let's rap about something, shall we? (Not that kind of rap, broski, the talking kind.)

Now, we all know what insane means, right? It's that guy who plays fiddle music in the background whilst he argues with his pillow about which government agency is actually targeting him, right? Well, okay, maybe that's a little hyperbole, and a lot of absurdity, but the point is: insanity is just NOT NORMAL; one may even say "abnormal," right?

Over a long period of time, humans have started to view insanity differently, from possession of a person's mind by evil spirits to structural decomposition and irregularities in neurotransmitter reuptake and distribution. Still, like anything that we've claimed so haughtily to know the secrets of -- or be close to knowing the secrets of -- people will still have varying opinions on it. So, choose one of the following four, explain why you think insanity is of that nature, and then do a little jig wearing a tinfoil hat:

1) Functional: Insanity is merely maladaptive behavior and habits that cause a person to be in breach of socially contracted normal behavior.

2) Structural: Insanity is a combination of physiological abnormalities and deficiencies that result in a change between the mind and body, leading to behavior and cognition that is not normal by a human baseline standard.

3) Functional-Structural: Insanity is a mixture of both behavior and physiology, resulting in the same as 1.

4) Extra/paranormal: Insanity is caused by outside, non-human forces, a form of divine ecstasy, or a way of viewing the world through a different, more open/closed mind.

Have fun!

As far as i know we have a fairly complete account of the causes for most mental disorders. You might as well have started a topic about cancer, and ask unqualified people for their opinion on it's causes.
Besides...

#1 doesn't really cover the origin of 'insanity'. Breach of social norms is usually one of possible symptoms of mental disorders, not their cause.

The answer is #2, as far as modern medicine can tell.

Hate to disagree so adamantly, but it's not like we've mapped out the entire human psyche or neurophysiology. Sure, we have a good idea of what causes insanity (I'm actually a #2 myself, but, hey, we've got some nuts here, right?), but there's always interesting opinions floating around to discuss; which I believe is the meaning for this board? :3

At any rate, I thought it would be interesting.