i've wondered the same thing... cuz i've done some pretty bad stuff :P but sorry i don't know really

I am a doctor.

That information definitely CANNOT be passed on unless:

1) You authorize it. This comes into play if you sign to  have your records released when applying to purchase insurance for example.

2) In cases of some serious crimes (usually felonies)

or

3) By court order (very, very rare)

HIPPA laws govern this privacy.

Hope that helps.

Being a minor might affect this-but since all my doctors have been in contact with my therapists("treatment team aghh) I have been ratted out when I told them about such compromising bad habits in the past.

Well... not necessarilly... If you pass on to the doctor some behaviors or thoughts that could put you or someone else in imminent danger the doctor is obligated to try to ensure your or a third party's safety.  This can include suicidality, or homicidality, or abuse of a minor.  Topics ie "self-destructive" behaviors are kind of a gray area... the key seems to be imminent harm. 

I don't think they can tell anyone, but they could use it to deny insurance claims, so I would still be carful what you say to a doctor.

HIPPA (confidentiality) Laws are very strict and do not allow confidential medical info to be spread around. If a minor were being abused authorities will be notified, If there is a threat of immediate harm to yourself or another authorities would be notified and you could be put in the hospital for immediate treatment. To give info to the insurance co you need to sign that paper, however if you don't give the insurance co permission to see it they'll probably deny you anyway. Several docs that are taking care of you may discuss your case to clarify the details and make it all make sense (this is to your benefit).

If a minor has issues about reproduction they can't tell the parents, however any other health problem that needs treatment they are required to get permission from the parent'

If the 'bad habit' you're talking about is an illegal substance (tobacco and alcohol for minors) docs don't ever tell anyone, you should tell them your habits however, so that they don't put you an a med that will cross-react with what you're taking.

If the bad habit is food (even abusing exercise/ or vomiting)- they know it or at least suspect it without you saying it.

I've met people who only tell their doc a detail here and then another detail there however if they had given all the details up front the correct diagnosis could have been made at the first visit without all the hassle of follow up visits/unnecessary extra tests.

Docs aren't out to get you - they really just want to make sure your are safe and healthy. They can do this better if you are honest with them and don't hide important info for fear of legal repercussion or insurance problems.