I'm hesitant about reproducing when i have a family history of mental illness. can i do anything to prevent this?

Not really but maybe: Unfortunate if there is family history of illnesses, expect the possibility that they may be passed down. However, you have to remember that this is just a possibility and not a guarantee. There are some recent studies that suggest that taking Folic Acid 1 month prior to pregnancy and into pregnancy can decrease the risk of autism by 40%. Educating children to get help early would work wonders.