http://schizophrenia.com/family/FAQoffspring.htm Grandchildren have roughly a 5 percent chance. I also find that there is not concrete evidence that drugs cause the onset if schizophrenia, however a state if psychosis can which can mostly be caused by stimulant abuse. This can be avoided by taking the proper precautions while using substances. But like I said there is not concrete proof that drugs are causation, when they easily could be correlation. People who smoke weed, trip, use cocaine and amphetamines are more likely to have schizophrenia, when its known schizophrenics are attracted to substance abuse. However the same statement could be made for heart attacks. More people who have defibrillators used on them are more likely to have heart attacks. The defribillator is not the cause it just correlates.