A study out of the University of Indiana, described on the BBC website today, reports that married people have better cancer survival than unmarried or those going through the stress of divorce, etc. This is apparently not related to the level or quality of treatment.
We note this report not because it is particularly singular on its own, but because it is one of countless studies, including placebo effects, that show the interconnectedness of our physiological systems. 'Psychosomatic' effects, often sneeringly denigrated, clearly occur. Genetically, there are connections between neural, immune, and endocrine systems. These may be the flags that show why such otherwise non-physical effects exist.
For research the implications can be profound. For many reasons, practical, cultural, and historical, reductionist approaches are at the heart of the current modus operandi of science. Maybe there are other methods, but for 300 years or so these have transformed science and technology and are deeply ingrained into our thinking and science training.
However, in this and many other ways, reductionist methods may draw attention too far down the causal chain. It could focus us on trying to isolate causes that can't be isolated relative to the function we're studying. A gene can be studied on its own perhaps, but if its interactions with other genes are what we're studying, our methods need to reflect that.
It's common and easy to criticize reductionism, and we're not doing that here, per se. However, old habits die hard. We've known ever since Darwin that all life goes back to a singular beginning, and genomic sciences show that rather clearly in terms of DNA mechanisms, sequence variation, and so on. What recent sequence data have shown is that mechanisms long ago established can be highly conserved over long evolutionary times. Traits long thought to be independently evolved are regularly found to be homologous in various ways, both deep and subtle.
Thus our attempt to parse systems into discrete modular subsets is ultimately doomed to be inexact. When and how a study of, say, immunogenetics, can be done on its own without considering, say, neurobiology, is not clear. We can't design single studies to cover everything, and reductionism is needed in any kind of study (you can't study genes without studying genes!). Similarly, holism is a term that often sounds clearer than it really is.
Evolution didn't care: what worked proliferated. Evolution by phenotype sorts organisms by their results, not caring about their specific causes. Since life today is due to common ancestry, the problem we see is in no way a surprise. But there probably should be more explicit and serious studies of how and where to 'reduce' and how to integrate.