My brother has been suffering from a mental illness from the last 8-10 years.. He has been on and off medication and seen multiple doctors.. Some he followed but most he disregarded.

At the start of last month (having been off his medication for nearly 9 months.. He was taking Abilify 30mg but not consistently and playing with the dosage) he seemed to have a psychotic break and we've taken him to the first psychiatrist he saw all those years ago and he said its a clear case of schizophrenia and put him back on Abilify.

A psychologist told us to seek a second opinion and the psychiatrist we spoke today said he definitely doesn't have schizophrenia but it is bipolar. We are really confused.. Is there any resources available to understand clearly the distinction between the two.. If there is one clear symptom that points one way or another?

To be clear, I am not looking for a diagnosis online. 

Thank you so much.. Sorry if this is not the right place for such a question.