This is a sensitive topic and I know that most people would recommend not discussing it. I used to be one of them despite having family members with mental health challenges.
However, the trend is changing. See the blurb from a dental student who works at Dental School Coach:
"I feel like the dental school world has opened the door to openly discuss mental illness in the past few years and made a big push to help students. My school alone has counselors that from day one come to us for lectures on burn out depression and anxiety and we have access to them and licensed therapists for free! A fellow student of mine also took time off for depression and was welcomed back the next year with open arms - I don’t know if you heard this story, but the last ASDA national chapter president who represented the entire country and all dental schools committed suicide a few years ago and since then, there had been a huge push to help students and talk about this and how to overcome this. I’ve attended the ASDA national leadership conference 2 years in a row and they have added a lecture series, 10 lectures a day almost for 3 days on various mental health topics and management. I think trying to hide it under the rug is not the greatest thing to do on an application especially with how dental school culture is heavily shifting now, but if an applicant wants to talk about how they overcome it and how they now help others with the same illness it could be great. Dental schools like mine are looking for clinicians that will know how to take care of and overcome their mental health so they can provide the best care for others. Just wanted to share my opinion!"
I think this comment is pretty profound. What you should focus on is how you have overcome that challenge and what are you doing to help others who are going through similar challenges.