Look at a long thread on health screening/questionnaire on Prospective student teachers forum. You will have to disclose all your medical history. If your uni's occupational health unit think what you've put down requires investigation, they will do so, by writing to your GP for a report, or inviting you for a talk with a nurse of a doctor. Don't worry about it though. A lot of people suffer from stress or depression from time to time - it's part of modern living - and most conditions aren't serious enough to cast a doubt over your mental fitness to teach. Just be honest in what you disclose, and it will be sorted out.