[Emilio Romero (OP)]

Is there any evidence to support that. Has there been any experiments?
How about schizophrenia?


thanks

[LeeE]

This question would probably do better in the Bio section, where you might get some proper bio scientists looking at it, rather than here in general science, but anyway...

I believe that some of the conditions you allude to only affect higher brain functions that may not be present in lower animals, so they wouldn't be susceptible to them.  Other conditions could be common between higher and lower order animals though, and regarding these I would guess that the effect would be to change the animal's behaviour, either conferring a survival advantage or, much more probably, a survival disadvantage.  If, for example, a rabbit were to suffer from bi-polar disorder, it might end up challenging foxes instead of running away from them, so it would seem likely that animals that do suffer from 'mental' disorders will be relatively rare as they'll be quickly eaten before they reproduce and pass on any tendency to the same condition to their offspring.

Of course, there's always the very slim chance that the bi-polar rabbit has such aggressive behaviour that it freaks out the foxes and survives to breed (until that is, as DNA pointed out, they reach the point where they think that the best way to deal with on-coming cars is to stare them out).