First results on the effects of MAO inhibition on cognitive functioning in elderly depressed patients

Elderly depressed patients who met the Research Diagnostic Criteria (RDC) for major depressive illness, were treated with phenelzine, a non-selective monoamine oxidase inhibitor, for a period of 2 to 7 wk, following 2 wk of placebo washout period. Possible pre- and post-treatment differences on the cognitive test battery were evaluated using the Wilcoxon test. Although recovery from depression was obtained in the majority of patients (Hamilton, Global and Self-rating Scales), none of the cognitive measures showed statistically significant changes over the course of the treatment period and the cognitive tests scores did not change as a result of treatment. It is of interest that tricyclic antidepressants (TCAs) are known to impair memory in geriatric patients, presumably due to their sedative and anticholinergic effects. The lack of an adverse cognitive effect for phenelzine therefore suggests a possible advantage of monoamine oxidase inhibitors over tricyclic antidepressants for the treatment of geriatric depression.