Individuals who have a family member with a mental illness have an increased chance of developing a mental illness, but the risk is slight. Scientists have not definitively determined what causes mental illnesses but they believe it is likely a complex combination of biological, environmental and psychological factors. At this time, it is simply not possible to predict who will develop a mental illness and who will not.
You did not mention whether you are experiencing mental health symptoms. If so, that would be a concern and you should be evaluated by a mental health professional.
You mentioned that your mother is currently not taking her medication because she “took herself off of it.” It is generally not recommended that patients stop taking medication on their own. It can and often does lead to an illness relapse. I would recommend making your grandmother aware (if she is not already) of the fact that your mother has stopped her medication.
Because mental illness has affected your family, it would be advantageous to educate yourself about the subject. There is a great deal of information available, via the Internet, about schizophrenia and bipolar disorder. Psych Central provides comprehensive information about mental health disorders. Two other reliable sources include the National Institute of Mental Health (NIMH) or the National Alliance on Mental Illness (NAMI). The latter is an advocacy group that assists families who have loved ones with a mental illness.
If you have additional questions, please don’t hesitate to write again. Please take care.