Functioning well as an academic is about having a brain that does stuff well. It's certainly not just about being clever, but there's no question that intellectual activity is the day to day activity of academia.
I wonder if that's a major reason depression is almost taboo in academia. Having depression is having a brain that doesn't work well in a significant way. Having your brain not working is not something you want to advertise if it's also what earns your income and respect.
I don't know if this is true or relevant. But I wonder.