I think one needs to be careful about looking at the saints’ lives and saying so-and-so had depression. I’m not saying it couldn’t be true, but it might be difficult for us non-saints (or saints-in-the-making?

) to actually know.
I mean, a non-Catholic could read the life of a saint and say, “Wow, a masochist with really low self-esteem.” But we know that’s not what was going on at all, but that actually, the saint was incredibly humble and close to God and wanted to abase him/herself before the unimaginable glory and holiness of God. There’s a spiritual reality that could vaguely resemble something profane on the surface, but is not at all related in actuality.
Many saints suffered from the “dark night of the soul.” This is NOT the same as depression. But somebody who didn’t know very much about it or didn’t believe in the spiritual reality might think it was similar or the same.
Part of the reason I feel caution is important is because many atheists (I know from experience, I’m surrounded by them!) will try to psychoanalyze the saints to show that they were pathological, hence “disproving” the Catholic faith. Mother Teresa is a good example. When it became known that she had suffered from terrible darkness in her soul for many decades, atheists said, “She was depressed! She was a hypocrite! She didn’t even believe in God!” Catholics who knew their faith said, “Saint.”