I am choosing not to disclose my diagnosis of asthma and ADHD (update: I read the DODI 6130 and the specifics of ADHD that would disqualify me do not apply to me) since neither affect me anymore and I can run several miles/do a full workout/hike without being affected at all.
I've been told that my doctors need to be listed on my HIPAA release form in order for them to check it or pull those records. What is your knowledge on this? and what are my chances of getting caught if I only ever get a secret clearance?
To give a US perspective, aside from the potential consequences to you and/or your comrades-in-arms in the event of a combat or hazardous situation, consider your last sentence. If you are wondering what your chances of getting caught are, then it sounds like you either already believe, or know, that you would not be eligible to serve if the service knew of your medical condition or conditions.
Considering that the training regimen is designed to both improve one's physical fitness, but also to weed people out, if you still suffer from asthma then it could flare up. It really depends on whether the asthma is under control, or if it is actually gone.
Also consider the potential repercussions or penalties that one might face, after one has submitted false or incomplete information to the federal gov''t. While it might be possible to slip through some of the cracks, at some point, someone is going to find out. Actually, someone it most likely to find out if you get involved in an incident and an investigation is then launched. In a case like this, the potential penalties for lying or submitting false information could easily result in an involuntary stay at Club Fed.