According to Rabbi Hillel Goldberg’s book on Rav Yisroel Salanter, as well as Rabbi Israel Glenn’s book, Rav Yisroel Salanter ZT”L suffered from depression, what was called by his talmidim as a “mara shechora”. He overcame it to become on of the most influential leaders klal yisorel has had in the last 150 years.
Most gedolim have dealings with people who have depression, as it’s very common- much more common than people are willing to let on.