More than 40 million American adults — almost 20 percent of the adult American population — will deal with mental illness this year. Yet mental health (of the citizens, not the candidates) has not been an issue in the presidential campaign. Hillary Clinton tried to change that last week, announcing a plan that offers hope for improving mental health research, diagnosis and treatment.

Central to Mrs. Clinton’s plan is the integration of physical and mental health care and reducing the stigma attached to mental health treatment.

Mrs. Clinton would direct the Center for Medicare and Medicaid Innovation to develop new payment methods for doctors that would encourage collaborative care by health care providers treating physical and mental health problems. She would also issue recommendations to spur private health plans to pay for collaborative care.

Mrs. Clinton also pointed out that though insurers have been required since 2008 to cover mental illnesses the same way they would cover physical ailments, enforcement has been spotty. Many mental health patients are forgoing treatment or struggling to pay for the care on their own.