The suppression of monoamine oxydase (flavin-containing amine oxydase). MAO is critical in modifying nerve-ending storage of certain monoamines (in this case, epinephrine, norepinephrine and dopamine...another type of MAO works on histamines), and MAO inhibitor drugs were, along with tricyclics, the first wave of anti-depressants. The problem was that if you ate brie cheese or chopped chicken livers while taking the drugs you could get a nosebleed or cerebral aneurysm...a double adrenergic whammy, since some foods are also strongly MAO-inhibiting (at least functionally). Although most current manuals (Merck's and Harrison's among others) consider these first generation drugs as safer and preferable to the recent Prozac and such, fashion am fashion, with docs as much as patients. Most of the patients a doctor sees are People That See Doctors (most Americans have infrequent medical contact).