Dolphin is completely wrong about schizophrenia. Genetics is the "fad" in modern science and there is no definitive link between schizophrenia and heredity. The cause(s) of schizophrenia (which is not a single disorder but a spectrum of them) is not known to medical science so there can not be any test genetic or physical for schizophrenia. Diagnosis of one of the kinds of schizophrenia is a purely subjective opinion of a psychiatrist.
Look up "schizophrenia" in a Yahoo! web search. Wikipedia has a good summary. Also read, John Horgan;"The Undiscovered Mind" how the human brain defies replication, medication and explanation: Free Press, N.Y. NY, 1999 to learn how little science knows about the mind and brain.
Stop worrying you're ok!
A 76 yr old schizophrenia paranoia patient diagnosed over 40 yrs ago who has been able to live a fairly normal life due to the TLC of family, friends, doctors and nurses. Med's. do help cope with the symptoms but do not prevent them.