Certainly the stigma regarding mental illness has decreased significantly over the last 50 years, but it's still there.

Whether you want to tell someone you have a mental illness or not is a personal choice, but if you do want to tell someone, but are afraid of a negative reaction, then it's problematic. It's problematic because it causes you to be fearful, and that causes a fight-or-flight syndrome to take place. Your hypothalamus will send cortisol and adrenaline coursing through your veins, and that's a good thing if you're being chased by a Wholly Mammoth for 5 minutes, but it's a bad thing to be chronically in this state. It will have a negative effect on every part of your body.

Thus if you want to tell someone you have a mental illness, but are afraid of a negative reaction, having that hard conversation may be in your best interest.

Usually those hard conversations end up being the easiest hard conversations you ever have.