Depends how bad your symptoms are, if your symptoms are not too severe it will make you sleepy for a fair few months before your body gets used to it, your body might never get used to the sedating effects. When the symptoms are very severe it takes them away which is a relief but barely put me to sleep or made me sleepy, just chilled me out. Some people react differently, but this is what happened for me and the people I have been in hospital with.

Yes it dumbs you down, every antipsychotic I've been on does. But again usually the symptoms are so severe I never had concentration to start with, and being 'doped up' on zyprexa was better than suffering like that.