Question: what are the main reasons why people have schizophrenia? 

Answer: Man, most of these people are severely misinformed about the causes of schizophrenia or schizoaffective disorders.  Cats walking in your food?  Non-vegetarian diets?  Give me a freakin' break...!\n\nSchizophrenia may affect the victim who has it in many different ways and on many different levels of severity.  One may be slightly schizophrenic, or schizphrenic to the point of loss of all social functioning and ability, i.e., it can be disabling.  It is characterized chiefly by paranoia, paranoid delusions, and/or hallucinations - either auditory or visual.  ANYTHING that can affect regions of the brain responsible for vision and hearing can then alter those perceptions and yield signs that would be diagnosed as schizoaffective, for example.\n\nPhysical damage directly affecting the brain can lead to behaviors symptomatic of schizophrenia (you fall down in the park and a stick goes through the roof of your mouth into your brain and causes brain damage, or you use drugs so much that it causes chronic physical overuse of seratonin receptors which results in cellular and functional brain damage are 2 examples of things that could happen physically).\n\nThere is believed (some evidence exits) to be a genetic component to being pre-disposed to having schizophrenia, but keep in mind that most people are not born with overt schizophrenic symptoms.  This suggests that it is more of a socially generated disorder, and is caused by gross misintrepretation of one's local and global environmental states coupled with his or her lack of self-esteem and self-confidence.  Someone with a lot of self-confidence will not become paranoid that everyone is talking about them, and are less likely, therefore, to show signs of paranoia, develop delusional thoughts about conspiracy, etc...all symptoms of schizophrenia.  Someone with no self-esteem or self-confidence, on the other hand, will be more likely to think everyone is against them, that secret agencies like the CIA are pitting conspiracy against them, and that others are plotting to hurt them in some way - since these things are not really happening (that is to sayt they are delusions), this individual will be diagnosed as schizophrenic when he tells these things to his psychiatrist.  There is interestingly the commonality among schizophrenic patients that the people that are out to get them are either secret agencies or large, powerful institutions - the CIA, the FBI, the government, the IRS - this is thought to be based on the fact that the victim needs to fulfill his paranoiad delusions somehow, and these organizations are not well known so it would be difficult for someone else to refute the fact that they are or are not after him.  That is, it's hard to prove that the CIA doesn't have a file on you, because if they did they wouldn't tell you.  This is referred to as "paranoid security", and is common among all schizoaffective patients.\n\nSo there are a lot of reasons one "gets" schizophrenia - the only common factor is that the causes are related to changes in brain chemistry, as I mentioned this is either physical or chemical in nature, and can have a variety of root causes.
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