True non-responders to either olanzapine or clozapine. True non-response is defined as: a) intolerance to either of the medications preventing an adequate trial, or b) only minimal (less than 20%) benefit with the adequate trial of either of the medications. Adequate trial constitutes at least 8 weeks of the medication with the dose of 20 mg on olanzapine or 200 mg of clozapine.