Bipolar and schizophrenia share a lot of symptoms...
Severe manifestations of bpd, schizophrenia and even drug psychosis look identical til EEGs and an MRI are done over several days.
Drug abuse can be seen in an MRI, the others to a lesser degree, but the EEG is definitive.
I'm not a doctor but have been through a lot with my fiance so have learned a lot. She was diagnosed at one point or another with all three of these. Turned out to be manic delirium, aka severe Bipolar I.
She did abuse drugs too (percoset in particular) but drug abuse was a comorbid condition with the bipolar (and later manic delirium) and didn't cause it. However all of it put together made it difficult to diagnose her correctly.