Yes, I can confirm that LCS has supported an emergency substitution due to mental health. For privacy reasons I don't think it's appropriate to comment on the specifics but we have verified the nature of this emergency and have notified competing teams.
Just as a wider comment -- I think mental health is extremely important in esports and in the LCS and it's something I personally believe we need to keep supporting. Earlier this year, we started discussing how we as a league can help with mental health overall in the LCS and in our development systems. For example... how we think about our formats (e.g. break weeks), working with players on their schedules (e.g. trying to avoid doing LCS-produced content on their 1 day off a week), having general mental health resources and more support, how we structure our academy/amateur development, and of course having mental health resources and support for our players... I think these are all things we'd like to invest in. A much wider topic for another time, but just know that supporting mental health is really important and a factor when it comes to decisions like this with a lot of nuance.