I wanted to write my common app essay on the panic attacks that I experience. It did cause my grades to lower slightly as my attendance was terrible because of these panic attacks. But I mostly want to talk about how I have used this experience to improve and now I truly value all opportunities and make sure I am always healthy enough so I don’t miss any valuable experiences and that I really value school more and I try a lot harder in everything I do, much more than before I had panic attacks. I just want to say that it made me a better person and that I have recovered from it. I also want to talk about how I used my experience to help my friends who experienced the same thing from committing suicide. I know talking about mental health is a big risk, but in this context do you think it would be ok to write my essay on this?
Maybe there is another topic that might be more appropriate.
In my opinion, I think it’s appropriate and it would make a good essay to talk about how panic attacks have allowed you to value your education more; however, although the part about suicide sounds compelling, it might be a bit touchy for a college essay. That also tells more about a particular instance rather than about you as a person. You could just talk about how panic attacks have led you to value everything more, then you could cover valuing life in general (which relates to the point I think you’re trying to make by talking about preventing your friend from committing suicide) and move more specifically into school throughout the essay. Just my opinion though 
I agree with beachykeen–your personal experience sounds appropriate for an essay, but the additional information about your suicidal friends seems a bit much. The essay is supposed to be about you, and with only 500ish words, branching out too much from your own experiences seems unnecessarily risky.
I agree with justonedad that you should find another topic. Panic attacks should not define you, especially for your college essay. You are so much more than that! I suffered from panic attacks when I was in my early twenties and I found that most people couldn’t wrap their heads around what I was experiencing.
As you can see from the responses here, they are varied.
The perception of you as a potential student may very well hinge on the background, opinion and outlook of the admissions reader, so you would be taking on some risk.
Be sure to carefully think this through.
Why is this something you want to highlight? I have panic attack, ADHD, and SAD for seasonal affected disorder.
I think the best way to answer this question is think of it this way. So you have one opportunity to let colleges know anything you want about you: what do you talk to them about? Find the answer to that and I think you will have found the answer to your own question.
I think the only way you should write about this is if overcoming this has taught you something important about yourself that you wouldn’t have learned otherwise or something similar. And in that case, I would downplay mentioning the panic attacks and focus on coming out the experience stronger. It would probably be to your benefit to pick another topic.