All Other Things Being Equal, Who Is Most Likely to Be

All other things being equal, who is most likely to be diagnosed with a serious mental disorder?

A) Robert, who has no family history of mental illness and feels as if his life is going well
B) Donald, who has no family history of mental illness but who is experiencing significant personal stressors
C) Gregg, who has a family history of severe mental illness and who is experiencing significant personal stressors
D) Michael, who has a family history of severe mental illness but feels as if his life is going well