


Mario thinks that I don't put much stock in the stress theory of disease, at least the way it shakes out in the average examining room, where stress is seldom triggered by an earthquake or holocaust but is usually a smaller-scale affair. Mario thinks that I have cast my lot entirely in with the competing germ theory, ascribing his past health problems to several debilitating H.I.V.-related infections and his current good health to a handful of strong medications. Mario thinks that I pooh-pooh the importance of his innumerable relaxation techniques in keeping him whole. And he knows that the last time stress loomed I made him do his blood anyway.

But what Mario doesn't know is that any thoughtful adherent of the germ theory of disease can only be impressed with how remarkably little it sometimes winds up actually explaining about infectious diseases. Not infection in the laboratory, among carefully selected populations of cells and animals, but infectious disease out here in the wild, where stressed-out humans often respond to germs in a way that defies the germ theory's simple axioms.

The unfolding story of the bacteria associated with peptic ulcer disease is a prime example. For years, ulcers were considered a paradigm of stress-induced disease, clear evidence of mental anguish turning physical. Then, a bacterium called Helicobacter pylori was linked to most ulcers, and the science swung around. Ulcers were only an infection after all. Psychology dropped out of the picture; relaxation was out for ulcer treatment, and antibiotics were in.

But strangely, the question of what causes ulcers remains almost as murky as ever. Many people carry H. pylori from childhood on, but more than 80 percent never get ulcers. Between 10 and 30 percent of ulcer patients never carry the bacteria. Meanwhile, scientific studies that convincingly associate ulcers with psychological stress remain to be dealt with. The German blitz of London in World War II and the 1995 Kobe earthquake in Japan both precipitated local outbreaks of ulcer disease. Studies have shown that ulcers heal more slowly in anxious people.

''Reports of the death of ulcer psychosomatics have been greatly exaggerated,'' experts concluded in The Journal of the American Medical Association last month.

A remarkably similar ambiguity already exists for many other infections: Germs both explain them and do not. Scientists still puzzle over why some people exposed to a cold virus get sick, while many others do not. Among the factors that seem to produce colds: long-term psychological stress, like losing a job. Among the factors that seem to protect against them: the social support of many friends and relatives.

Before Robert Koch discovered the tubercle bacillus in 1882, theories ascribed tuberculosis to everything from stress to genes to bad air. The bacillus seemed to void them all, but only temporarily: For every 100 people exposed to the tubercle bacillus and infected by it, it turned out that only 10 got sick. Scientists have spent most of this century trying to make sense of why that is so; genes, luck or stress.

A nascent germ theory of heart disease is now making headlines. Traces of an organism called Chlamydia pneumoniae have been found in the sludge within diseased coronary arteries; when rabbits and even some humans with heart disease are treated with antibiotics active against chlamydia, their heart disease appears to improve.

But the discovery of a heart germ is unlikely to resolve the many mysteries of heart disease, or erase the strong evidence that stress, depression and personality type appear to be cardiac risk factors, just like cigarette smoking and blood lipids. Heart medications may come to include antibiotics some day, but the endless jostling of the psychosomatic and the orthodox theories of disease will continue.

Acolyte of the germ theory that I am, I almost bet Mario $20 last month that the stresses of a new job were not somehow going to inactivate his medications and give his infections the upper hand. Fortunately, I restrained myself. The blood tests I made him take came back completely out of whack. I was not looking forward to seeing him again and admitting defeat.

But Mario, stressed no more after passing probation at his job, synthesized it all a few weeks later with elegant simplicity.

''I told you I was stressed,'' he said. He paused. ''I was really stressed.'' He paused again. ''I was kind of too stressed to take my medicines for a while.'' He smiled sheepishly. It was another split decision.

Drawing (Tom Bloom)