Here’s something I read recently in a blog post (The Limits of (Neuro)science at Neuroskeptic) that started me thinking: “Will science ever understand the brain? … The notion that humans are complex and hard, while nature is easy, is an illusion created (ironically) by the successes of reductionist science. Some of the biggest questions facing mankind for eons have [been] answered so well, that we don’t even see them as questions. Why do people get sick? Bacteria and viruses. Why does the sun shine? Nuclear fusion. Easy.”

I started to write a simple reply, but it grew into the following.

Medicine is an applied science, not a pure science

It may be true that understanding the human brain is only an order of magnitude more difficult than understanding any other aspect of human biology. I’m uneasy, however, about putting ‘why people get sick’ in the same category as ‘nuclear fusion.’ Particle physics is a science. Questions can be asked and (usually) answered under the controlled conditions required by the objectivity that characterizes science.

Medicine is the application of certain sciences (molecular biology, biochemistry, medical physics, histology, cytology, genetics, pharmacology, neuroscience) to – ultimately — individuals. Each individual is the product of a unique, lifelong sequence of social, cultural, economic, and psychological (as well as physical, chemical, biological, and genetic) influences. To this day, we don’t really know why some people get sick and others do not. To my mind, that makes medicine an application of science – like engineering – not a science in itself.

Take bacteria and viruses. It’s true that pathogenic bacteria can make people sick, but what’s interesting is that they don’t always. Inspired by the germ theory of disease, medicine in the late 19th century held that a specific disease must have a single cause. The cause of tuberculosis was the tubercle bacillus: if you had the ‘germ’ you must have the disease. By the 1930s, medicine began to acknowledge that diseases could have multiple causes. And by the mid-20th century, medical textbooks explained that the presence of the tubercle bacillus did not always lead to TB. The bacillus was a necessary ‘seed,’ but the patient was the ‘soil’ in which the seed might or might not grow.

Does the scientific nature of medicine limit its potential?

I admit there may be large, indefensible holes in the assertion that medicine is not a science. How different is it from geophysics, which studies the earth and its environment (including the earth’s climate)? Isn’t that a science? Yes, because it adheres to the scientific process of measuring observable data, publishing the results for peers to review, and not giving credence to mere opinion. Surely the same could be said of medicine.

My real objection to medicine as a science is that by focusing on what can readily be quantified, it ignores what cannot, such as the social determinants of health and disease. Medicine’s historical desire for the respectability that comes with being a science gets in the way of discovering what could actually make us healthier.

Health care does not create health

Although we don’t know why some people get sick and others do not, we have some ideas. It could be what we eat, the quality of the air we breathe, our occupation, how much we earn, whether we feel our situation in life is fair, how we were treated as a child, numerous sources of stress in our lives.

Science prefers to isolate and understand one thing at a time, but the ideas I just mentioned are difficult to separate from their social context and cannot readily be studied in a controlled environment. The topics for medical research that seek and receive funding are those that investigate ‘reductionist’ theories of disease: things that fit neatly into categories sanctioned by the medical establishment and that can be readily measured, compared, and replicated. The cause and effect relationship between stressful living conditions and the health of individuals does not fit neatly into any simple mechanical model with the potential to make successful predictions.

For political reasons, it’s safer for medical research to stick to the limited agenda of what’s easily measured. If researchers investigated the social determinants of health, the answers could prove disruptive or inconvenient for prevailing economic (and thus political) interests. I’m thinking here of things like reducing air and water pollution, keeping carcinogens out of the food supply, and making sure drugs are safe before they’re prescribed for a large segment of the population. (The negative externalities of corporate culture, in other words.) It’s quite likely that social determinants of disease are extremely important for health. We don’t know for sure, not only because they’re hard to measure reliably, but because pursuing them tends to be politically unpopular.

Health care systems, informed by the scientific categories of medicine, are not designed to deal with things that cannot be easily quantified. Health care policy is set by politicians whose financial interests have been known to trump the common good. What preventive health care is good at these days (as opposed to the days when there was time for the doctor-patient relationship to offer comfort and relief) is creating guidelines for unacceptable levels of blood pressure, cholesterol, or blood sugar and prescribing drugs when tests indicate a patient has crossed an arbitrary but measurable threshold. That, and shift the blame for poor health onto the lifestyles of individuals, and be very expensive.

This is short-sighted.

A society that spends so much on health care that it cannot or will not spend adequately on other health-enhancing activities may actually be reducing the health of its population.

We need to figure out a way to liberate health from the financial interests that drive health care. Until then we’re stuck with a system that cares more about profiting from the narrow agenda of scientific medicine than it cares about improving health.

Jan Henderson is a historian of medicine who blogs at The Health Culture.

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