Sri Aurobindo
Letters of Sri Aurobindo
Volume IV - Part 3
T.B. is the result of a strong psychic-vital depression. Sex cannot 
directly cause T.B. though it may be a factor in bringing about a fall of the vital forces and a withdrawal of the psychic supporting forces leading to T.B. The lack of vitality which easily comes as a result of modern civilisation is therefore a very strong contributing cause. Moderns have not the solid nervous system and the natural (as opposed to the artificial and morbid) zest of life that their ancestors had. But I don’t know about the soldiers – the hideous trench war with all its ghastly circumstances and surroundings was, I imagine, far more difficult to bear than the open air marching and fighting of the Napoleonic times.