Graham Rook is emeritus Professor of Medical Microbiology at UCL (University College London). He was educated at the University of Cambridge and at St. Thomas’ Hospital London, becoming Professor of Medical Microbiology at UCL in 1994.

The theme of his research was initially the immunopathology of tuberculosis, but in recent years Graham’s focus has been the application of a Darwinian perspective to the effects on health of diminishing exposure to microorganisms (including mycobacteria) from the natural environment, and of the changing composition of our symbiotic microbiota.  

Graham coined the expression, ‘Old Friends Hypothesis’ to highlight this Darwinian re-interpretation of the ‘hygiene hypothesis’ in 2003. Initially the ‘Old Friends Hypothesis’ was focused mostly on chronic inflammatory disorders such as allergies and autoimmunity where there is a clear malfunction of immunoregulation. 

More recently, in collaboration with neuroscientists and psychiatrists, this thinking has also been applied to certain forms of depression and other psychiatric disorders that are accompanied by persistently raised biomarkers of inflammation. In particular, he is applying the Old Friends mechanism to the reduced stress resilience of people living in high-income countries.

Watch Graham at TEDx

Graham’s approach is interdisciplinary, with emphasis on integrative physiology, leading to publications on endocrinology, immunology, microbiology, psychiatry, oncology and neuroscience. 

Graham’s research has led to more than 300 peer-reviewed publications listed in PUBMED and more than 80 other reviews, books and book chapters.  Many of these, and also media appearances and interviews, can be accessed via his website.

He is currently editing a major review of the entire subject in book form, bringing together experts on the field from across the world.