Richard Is 16 and His Older Brother Tommy Is 18

Richard is 16 and his older brother Tommy is 18.Their oldest sister is in her twenties and is showing signs that the doctors now believe are related to schizophrenia.Richard,Tommy,and their friends enjoy relaxing by holding blues-based guitar jam sessions and smoking marijuana.How might this affect Richard and Tommy's risk of developing schizophrenia?

A) It will double their risk.
B) It will not have an effect.
C) It will increase their risk by 25%
D) It will depend on whether they continue to smoke marijuana into their twenties and thirties.