Horizontal studies are so hard. There is so much modern medicine can't always incorporate into studies that are confounders.

For example the gut brain connection is not well understood. Links between autoimmune responses to cancer can cause all kinds of problems that can seem unrelated(an example is myotonia which appeared in one of my relatives a full year before their breast cancer diagnosis and went away after treatment). I recently read in the times an article about the discovery of another circulatory system apart from the one we have; apparently acupuncture may get a more scientific and serious look into because it interacts with that system. There is also the business of how psychiatry schools still are not teaching how to not treat the brain as if it's an isolated organ, a wholisiti approach is being only now taught in all but a handful of schools(I think this was in the economist).