Will have to get back on you about the genetics of schizophrenia, but (from memory) it does have a genetic component. However, monozygote twins show at best 50% correlation of disorder. This indicates that it is NOT a given that it will transmit through generations.
Genetics works hand in hand with the environment and cognition in these cases so to point to any one 'cause' is impossible.
With OCD and cog distorts we all (i.e. every human being) have a genetic predisposition as a species to develope these behaviours (it's part of social learning of cause and effect) and cognitions. We are all very prepared to learn to be afraid of spiders for instance.
Growing up in a house hold where every one uses phrases like "touch wood" to ward off ill luck or not opening an umbrella in the house (because it will bring bad luck) will transmit that behaviour across generations. We learn it. Thats what humans do. We are the best learners on the planet. Sometimes (often) we learn to believe the wrong things.
Supperstitous behaviour is just like OCD. We try to control what we percieve we need to with some form of ritual that we have 'learned' will increase our control (washing germs away etc). Whether this actually works does not matter. We learn to believe it works. Like a magic spell, a ritual or a prayer. We can't prove it does not work and we fear to take a chance (by not performing the ritual) that it does not work.
Here is something to think about. The prayer some people offer to they're gods could be seen in exactly the way I have described above.
Ed: Checking profile update
This message has been edited by Larni, 04-12-2006 05:21 AM