Treatment-resistent depression in the elderly.

1. Male or female inpatient;

2. Aged 60 years or older;

3. Meet the DSM-IV criteria for major depression, single or recurrent episode (296.2x, 296.3x);

4. Non-response to adequate treatment with a tricyclic antidepressant (minimal 4-6 weeks with serum levels within therapeutic window) or venlafaxine (minimal 4-6 weeks with a sum serum level of venlafaxine+ O-desmethylvenlafaxine > 200 microgram);

5. Have a baseline total score of at least 20 on the MADRS;

6. Have a MMSE score > 15;

7. In the opinion of the investigator, have sufficient intelligence and motivation to comply with, and is competent to understand, the study procedures (especially dietary instructions in case of phenelzine);

8. Sign the written informed consent.

1. Known hypersensitivity to lithium or phenelzine;

2. Previous unsuccessful adequate (minimal 15 mg during 4 weeks) treatment with phenelzine or with lithiumaugmentation (minimal serum level of 0.6 mmol/l during 4 weeks);

3. Use of lithium or phenelzine within 30 days prior to baseline, use of a MAO inhibitor within 14 days, use of fluoxetine within 21 days, use of any other psychotropic drug (except antidepressants and those allowed during the study as concomitant treatment) within 7 days prior to baseline;

4. The presence of a physical illness which serious interacts with treatment with either lithium or phenelzine;

5. Alcohol or drug abuse within the last 2 years, according to DSM IV criteria;

6. Presence of dementia or non-affective psychotic disorder, history of bipolar disorder (I and II);

7. Concomitant use of alcohol or drugs that can have serious interactions with phenelzine or lithium.