sentences:  In one study, the risk of bipolar disorder, particularly for early-onset disease, is J-shaped, with the lowest risk for children of 20- to 24-year-old fathers, a twofold risk for younger fathers and a threefold risk for fathers >50 years old.There is no similar relationship with maternal age.A second study also found a risk of schizophrenia in both fathers above age 50 and fathers below age 25.