I don't think I agree... to be diagnosed with Schizophrenia, one has to show dellusions/hallucinations for a period greater than 6 months...
Everyone can have a psycotic episode triggered by depression, stress and specially drugs. However, in Schizophrenia, the psycotic episodes are recurrent and not necessarily triggered by anything.
It is also a disease that starts when the individual is very young... They demonstrate a schizoid personality - those distant, introverted kids who have a very hard time forging emotional/social connections.
Not all shy kids are going to develop schizophrenia, however, it is very rare that a extrovert kid that is full of friends will develop the disease.
Like depression and other mental illnesses, there are varying levels of the disease. Some people are able to function very well and have mild attacks, while others are almost incapacitated.