I've read a little about Darwin's long-term health issues, and the treatment he sought for them. What I want to know is what are currently considered to be the most likely causes of his ill health. Have there been any theories about it which have gone out of fashion? Is there a single, widely accepted theory? Or is the cause still wide open to speculation?
Theres no central authority who controls this obviously. So the theories seem to change a fair bit. I dont know that anything I've read of late is specifically and clearly authoritative enough to give you answer to this.
Chrohns Disease http://rsnr.royalsocietypublishing.org/content/61/1/23.full Melas Syndrome http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3632469/
These are all viable options and most of the more reasonable papers admit a degree of speculation in their conclusions. I'd still consider it wide open to speculation.