Psychosis can sometimes be a symptoms experienced as a PART of mania. Here is what they say about it on the National Association of Mental Health:

"Psychosis: Sometimes, a person with severe episodes of mania or depression also has psychotic symptoms, such as hallucinations or delusions. The psychotic symptoms tend to match the person’s extreme mood. For example:

Someone having psychotic symptoms during a manic episode may believe she is famous, has a lot of money, or has special powers.
Someone having psychotic symptoms during a depressive episode may believe he is ruined and penniless, or that he has committed a crime.
As a result, people with bipolar disorder who also have psychotic symptoms are sometimes misdiagnosed with schizophrenia."