Depends on the friend. Usually I'm more than okay with discussing things about mental health with friends.
I've had a couple very ill friends who struggled with bi-polar disorder where eventually I needed to limit/end our engagements because they became abusive.
Both opted to not continue actively seeking therapy and discontinued taking their much needed medication.
With the second friend, based on my past friend experience I had expressed clearly I needed them on meds and in therapy if they were to continue being in my life. Both didn't feel they needed either and I couldn't/wouldn't let them continue to be verbally abusive to me.