The medicals for the Forces are very thorough, and do require some delving into your past medical history. There's no-way you can legally "erase" things from you medicals records, however, you can be ready for when they question you. i.e. "I was feeling under pressure at school, my parents weren't being too supportive, and so I felt something might have been wrong with me. Experience has now lead me to believe that there wasn't anything wrong medically, and I have now learned to deal with stress effectively."