A Clinical and Genetic Study of 1,280 Cases of Mental Defect
- Author:
Penrose.
Medical Research Council. H.M. Stationery Office. 2/6.
The research now reported upon by Dr. Penrose has been carried out under the joint auspices of the Medical Research Council, the Darwin Trust, and the Royal Eastern Counties Institution, and represents six years’ work. It is scarcely necessary to say of any research carried out by Dr Penrose that it has been done with scrupulous regard for detail and accuracy. The family of every case, we are told, was visited on the average twice or thrice by members of the staff engaged in the research and a mental assessment of each relative who could be found was made. Records of public bodies, general and mental hospitals were consulted. Complete accuracy of assessment could not, of course, be expected, and results, Dr Penrose warns us, must not be regarded as of more than approximate accuracy, but this is more than can be said of some past enquiries into the same subject.
Taking the cases purely on the basis of mental grading, it transpired that out of the parents of the 1,280 children?and only 95 could not be traced?146 of the mothers and 49 fathers were judged defective?a percentage of 7.6 in all, but the percentage varied with grade from 12.1 among parents of the Feeble-Minded to 2.7 for idiots. Sibs of idiots also tend to be more intelligent than sibs of the Feeble-Minded, although among the sibs of idiots, idiocy itself is also more frequent.
A large section of the report is devoted to inheritance in relation to the various clinical types found among the cases?Mongolism, congenital syphilis, neurological and other abnormalities, epilepsy, psychopathy. In Alongolism there would appear to be some genetic basis. The chance of finding a case of Mongolism among the relatives of Mongols was found to be ten times as great as when the patient is not a Mongol. Dr. Penrose appears to be satisfied that congenital syphilis may be a definite cause of mental retardation, even the only cause in some cases. The relationship between diplegia and mental defect it is not yet possible to define, but the fact that in some families only the diplegias were defective appears to suggest some genetic relation between the two conditions. On the other hand, the diplegic sib of a diplegic defective was not always defective and among sibs of diplegics, appeared diplegics who were normal in intelligence.
With Tredgold, and in opposition to Berry, Penrose accepts microcephaly as a separable type. One microcephalic had two similarly affected sibs, another had one, and two microcephalic patients were twins. He finds some evidence for a single recessive gene in some of these cases.
In the residual or sub-cultural group occurrence of defect among parents and sibs was more frequent than among the rest. There was also less difference between the mental grades of patients and those of their parents and sibs in this group than in the clinical.
These are only a few of the large number of interesting findings reported. There are special sections dealing with parental consanguinity, maternal age and sex-linkage.
The general result is that evidence was found of recessive inheritance in six clinical conditions, dominance in three others, and in still others there was evidence of specific family concentration which does not necessarily mean hereditary causation. In the residual group a more probable theory is of a combination of factors. What does appear to be made clear by the research is that the genetics of Mental Defect cannot be studied satisfactorily in the mass but only in relation to individual types. Dr Penrose concludes with a reminder of the role played by environment. ” The aetiology of Mental Defect,” he says, ” is multiple, and a facile classification of patients into primary or secondary, endogenous or exogenous, cases would have only led to fictitious simplification.” H. H.
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