Sheryl was diagnosed with bipolar when she was a teenager shes hesitant to tell her friends and tries her best to hide

Sheryl is doing this because she is afraid of their reaction and unfortunately that is because bipolar disorder is one of the stigmatized illnesses. You can define stigma in few ways like something that is a perceived negative attitude, a mark of shame that distinguishes one from the rest of the society and based on that people are unduly discriminated against and they can feel devalued as a result.