They will ask on your license application if you have had a mental illness and to what extent it impairs your performance. This varies from state to state though some states just ask if you have any illness which could impair your performance this includes mental illness. The ADA act will not protect you if you don't get a license. Also if you lie on your application your license can be revoked. Basically you will be at the mercy of the state and may even be given a probationary license. If you have an involuntary commitment the state already knows so you will have to say yes , explain, and hope for the best.

A friend of mine has epilepsy and finished med school. When she asked for a break becuase she thought she was about to have a seizure they told her no and asked what medicine she wanted if she did seize. So don't expect any special treatment or protection from the ADA.