Mr. A was a white, 59-year-old man whose approximately 6-year history of depression (characterized by despondency, fatigue, anhedonia, crying bouts, and anorexia) followed the death of his mother; he had never sought treatment. Approximately 2 months before seeking consultation, he began to experience increasingly severe paranoid delusions that he was being monitored by video cameras in his home, that his food was being tampered with, that he was being followed, and that his life might be in danger. His baseline scores on the 21-item Hamilton depression scale and the Brief Psychiatric Rating Scale (BPRS) were 33 and 73, respectively.

Results of routine laboratory analyses revealed no abnormality, and the medical history was unremarkable. Various treatment options were reviewed, and olanzapine was suggested for treatment of the prominent psychotic symptoms because of its favorable side effect profile. The plan was to initiate olanzapine treatment and subsequently add an antidepressant as needed. Mr. A had been reluctant to take medication but consented to start a regimen of olanzapine, 5 mg/day. There was no significant change in the depressive or psychotic symptoms after 1 week, so the dose was increased to 10 mg/day. The drug was well tolerated, with only mild dizziness and nausea noted at the higher dose. Orthostatic blood pressure was within normal limits. Four weeks later, Mr. A began to question if he was really being monitored by other people or whether it was all in his mind. He was less motorically retarded and more verbal and reported feeling better. By week 6, his Hamilton depression scale score had dropped to 13, and his BPRS score fell to 38. Beck Depression Inventory scores fell approximately 34% during this period. His family confirmed substantial improvement in Mr. A's activity level, mood, and paranoia.