Causes of Disease

Abstract

All disease has one of two causes: the genes or the environment (Table 2). In general, the more severe the consequences of a missing or faulty gene are, the rarer is the incidence. This is because those afflicted with a severely debilitating disease tend not to raise a family and therefore do not pass the gene on to the next generation. This is particularly true of the diseases that lead to death before maturity. Such “bad” genes are maintained in the population only because they are passed on by carriers.