Bailey is not impressed by this decision and starts exhibiting some odd behaviors, later she is diagnosed with OCD after what happened with the CDC investigation. Though initially resistant to see a therapist and take medication, Bailey is able to resume her surgical career.

What mental illness does Miranda Bailey have?

Miranda Bailey, an attending surgeon living with obsessive compulsive disorder (OCD).

What's wrong with Bailey in Season 5?

Cancer. ... They finally diagnose her with cancer. She doesn't want anyone to freak out, so she tells Cristina because she needs to tell someone and Cristina is "a robot." Cristina helps her with treatment, but when Izzie refuses treatment, Cristina tells Bailey and soon everyone knows.