meth and schizophrenia?

[nirvana]

i was talking to my friends stoner brother whos pre-med. fun
and amusingly common combo, huh? the night before, he
came home stoned when i was sleeping over at his house, and
me, him, and his sister were eating munch 'ems and talking to
their mom (why cant my mother be like this) in a pupil-dialated
stupor.
the next day, we were talking about random shit and i
mentioned that my great-grandmother had extremely severe
schizophrenia and subsequent psychosis. to give you an idea,
she did not know she was pregnant and gave birth to my great-
aunt in the bathtub.
[side note]ever since i found out about her schizophrenia and
figured out what it meant- when i was about 9 or 10- i have
been terrified of it. both my parents being doctors, i have
learned fun facts about how most mental illness- schizophrenia
and bipolar disorder included- is thought to be genetically
linked. i seriously have a major pre-occupation with this
disorder. i look up symtoms and treatments. watch movies like
a beautiful mind and donnie darko for (in)accuracies. i even
wrote a story called schizophrenic love affair from the
perspective of the voice in a teenager's head. [end side note
haaha]
anyways, my friends bro decides to enlighten me about use of
drugs in relation to schizophrenia, amphetamines in particular.
he proceeds to caution me about the use of any hard drugs. i
asked him to define 'hard.' he uses a rather constrictive but
appropriate description, for someone who smokes as much
weed as he does, at least. his hard drugs: anythign except
weed and alcohol. he is drawing the conclusion that i have
done more drugs than these and further cautions me about
crystal meth inparticular. this freaks me out. the fear has also
caused me to abstain from use of adderal, somethign popular
and cheap where i live.
i sort of have a personal goal to do a lot of stuff between now
and the time i die, and i dont have the greatest self-control. it
took a lot of using anything before i could accept when i was
good and not turn into an innebriated, semi-conscious idiot
because i couldnt pass up just one, two, five more. i was
wondering if anyone else has heard of the correlation between
schizophrenia and meth, and if they have, how probable is it?

thanks, and sorry that was so ridiculously long.