Although we are grouping mental and neurological diseases together, the fact that there’s overlapping symptomatology is deceptive because we’re dealing with a diversity of diseases, many of which are very common. Just how common mental illness is depends upon who did the survey, when it was done and what criteria are used. Some of the results tax credibility. In 1962 it was reported that 81.5 percent of Manhattan’s residents showed signs of mental illness. Were the epidemiologists from New Jersey or Connecticut? The figures seem somewhat skewed!
Table l.RELATIONSHIP OF DOWN SYNDROME TO MOTHER’S AGE