I have a friend that was diagnosed with "manic depression" and she says alot of times just before she goes into "an episode of mania", she experiences the smell of CHalk. I thought that was interesting.. It's kindof like a harbinger (sp?) for a manic episode for her. I asked her if that happens, can she increase the medicine, etc.. and she said it usually doesn't help, that it will happen pretty soon after that sensation... The brain is so complicated and yet fascinating at the same time.. This could be some form of an "olfactory hallucination"? I wonder if any studies have been done on this?