My expsreince has been lying/stealing associated with mania in my daughter.It was the mood disorder. She is more stable now and while I donot really beleive everything she says, it is much better.
I found that boudnaries are imortant. Oh and impulsiviity huge factor. I do have to lock everythng,etc.
In my expereince, s=could not reason. In our expereince with my daughter, it was illness, not a moral issue. Lectures for hours did nothing. I cannto rason. I do not react. I focus on stabiity and prosocial. Compassion