• Hamilton-Depression-Scale- HAM-D [ Time Frame: 14 days ] [ Designated as safety issue: No ]
  

• rate of remission (HAM-D less or equal 7) [ Time Frame: 14 days ] [ Designated as safety issue: No ]
  
• differences in HAM-D total scores [ Time Frame: 14 days ] [ Designated as safety issue: No ]
  
• differences in MADRS (Montgomery Asberg Depression Rating Scale)and CGI (Clinical Global Impression)scores [ Time Frame: 14 days ] [ Designated as safety issue: No ]
  
• predictive value of HAM-D subscales for treatment response use of comedication [ Time Frame: 14 days ] [ Designated as safety issue: No ]
  
• survival in study [ Time Frame: 14 days ] [ Designated as safety issue: Yes ]
  
• differences in rates of adverse events, weight [ Time Frame: 14 days ] [ Designated as safety issue: Yes ]
  
• differences in HAM-D scores and survival in extension phase [ Time Frame: 2 months ] [ Designated as safety issue: Yes ]
  

The study is using a randomized double-blind, parallel-group, placebo-controlled design. 30 patients per treatment group will be included into the study and randomized to the treatment groups using a computer program. Psychotic features of depression will be excluded by a score of 2 or less in the PANSS subscales P1, P3 and P6. Treatment resistance as defined by history of non-response to two antidepressants from different classes at an acceptable dose and period is confirmed retrospectively. If possible, treatment compliance should be confirmed by plasma level examination. After informed consent, visit 1 is performed on day 0 (inclusion criteria, history, demographics, physical examination, vital signs, HAMD, MADRS, CGI, lab). Study medication is started on day 1, the antidepressive therapy is continued at stable dose until the end of the study. Patients will receive a double-blind therapy of either 10 mg/d olanzapine or placebo. Study visits will be performed on days 4, 7, and 14 (visits 2-4: vital signs, HAMD, MADRS, CGI, lab).

After 14 days, the patients will be classified as responders or non-responders. A responder is defined by a reduction of the initial HAM-D score of more than 50%. Study treatment will be stopped in non-responders and continued in a double-blind manner in responders for further 60 days. Thereafter, the the study medication is stopped and the patients are observed for further 14 days. Study visits will be performed every 14 days. This extension phase was added to examine if a prolonged treatment with olanzapine could ensure a sustained treatment effect. It should be excluded that olanzapine has a short-term tranquillizer-like effect or leads to unfavourable medium- to-long-term depressiogenic effects as observed with other neuroleptics used in depression ( e.g. fluspirilene). Moreover, withdrawal effects should be excluded.