This is not an ethical question (nor an ehical question). But the question of self-disclosure is a great one. Here are my thoughts:
1. medical students are often taught to be dispassionate, maintain boundaries, and not share things with patients. This is even more extreme in psychiatry. Well, the reality is one can share whatever you feel comfortable sharing and that is how to decide what to self-disclose. but there is a time and place for everything. I would argue that an inpatient psychiatry unit is not the place to be telling patients you have bipolar disorder.
2. It is your inexperience and difficulty knowing how to connect with patients in the horrifically traumatic environment of an inpatient unit that is making you ask these questions. If you have bipolar disorder yourself, it may be even harder still for you to work in this environment. But if you can't figure out how to establish rapport with patients than telling them "I'm one of you", well then that is what you need to work on. Telling patients you have bipolar is a lazy way of trying to build rapport and has the chance of spectacularly backfiring.
3. Just because you have bipolar does not mean that you know what it is like to be in the patient's position. You do not. Their experience is not your experience and you can never know their experience, all you can know is your experience of their experience. It is dangerous to make assumptions that you do.
4. There is a power dynamic set up in the hospital setting that is even more stark than in an outpatient setting. You have the keys to the asylum. Your patients do not.
5. You telling patients you have bipolar disorder could elicit a number of reactions: maybe it could offer some hope to patients; but for others still will react with feelings of shame, and believe they aren't doing well enough, or feel you are chiding them or criticizing them for being ill. Others still may react with anger or hostility projecting their own rage for their illness upon you "why is this mentally unstable lunatic my doctor?! I'll report him/her to the medical board!" etc.
6. It is not about you. When you start talking about your experiences, you unavoidably make it about you. We are here to focus on our patient, and their experiences, and not your need to reconcile this unbearable feeling of straddling the line between being a mental patient and being a physician (imposter) in a looney bin.
7. When patients are very manic, very psychotic, decompensating from their personality disorders it is not possible to establish rapport. There is no therapeutic alliance. It makes it so much easier when you accept that fact.
8. Therapeutic alliances are even more tenuous on an inpatient psych unit if a patient is involuntary.
9. Sometimes patients do need touch. Hugging patients is sometimes okay. I used to hug patients all the time on medical units when I worked in internal medicine. In psychiatry, I almost never hug patients (in fact I only hug them if they initiate and we have the chance to talk about what that is about). It is rarely appropriate to hug patients on an inpatient psychiatric unit. You must be very careful about being incorporated into the delusional system of patients, of being accused of sexual assault etc. How much did you need to hug the patient because you had no idea how else to respond to the distress of this suffering patient? What happens if a patient repeatedly expects to be hugged? What if a patient wants more than a hug? This is why it is important to understand some of the aspects of this. At the very least there must be another member of staff present to protect you and your patients.
10. Mental illnesses are not just like physical illnesses. They just aren't and no one believes otherwise despite lots of campaigns to try and medicalize misery. Mental illnesses impact the experience of the self - your thoughts, feelings, perceptions, behavior - (put simply your soul) in a way that other illnesses to not. They are also not diseases (and btw hypertension is not a disease, it is a risk factor). This is one of the reasons there are all sorts of other considerations that you would not have to consider with diabetes etc.