There is a form of illness, very widespread today, which was hardly known a hundred years ago — nerves or neuroticism — not because it was unrecognised, but because it was so uncommon. This characteristic illness springs from the materialistic outlook of the eighteenth century. Without that, the illness would never have appeared. The occult teacher knows that if this materialism were to continue for a few decades more, it would have a devastating effect on the general health of mankind. If these materialistic habits of thought were to remain unchecked, people would not only be neurotic in the ordinary sense but children would be born trembling; they would not merely be sensitive to their environment but would receive from everything around them a sensation of pain. Above all, mental ailments would spread very rapidly; epidemics of insanity would occur during the following decade. This was the danger — epidemic insanity — that faced mankind, and the possibility of it in the future was why the leaders of humanity, the Masters of Wisdom, saw the necessity of allowing some spiritual wisdom to be diffused among mankind at large. Nothing short of a spiritual picture of the world could restore to coming generations a tendency to good health.
Source: Rudolf Steiner – GA 95 – At the Gates of Spiritual Science: Lecture 7: Workings of the law of karma in human life – Stuttgart, 28th August 1906