The British Medical Association and the Prevention of Mental Deficiency
A discussion on the prevention of Mental Deficiency occupied, as we an- nounced in our last number, one of the sessions of the Annual Meeting’ of thv, British Medical Association held at Bradford in July.
The discussion was opened by Dr Tredgold, who said at the outset that our capacity to devise any effective method of preventing mental deficiency depended uP?n our knowledge of its cause, and that it was therefore on the subject of causation that their debate must chiefly be based. The essential cause of primary?as distinct from secondary?amentia was a diminished developmental potentiality of the cerebral neuroblasts; this was germinal in origin, and was inherited and transmissible. It might, therefore, seem that to prevent mental deficiency all that was necessary was to prevent the propagation of defectives by means o segregation or sterilisation, but the matter was not quite so simple as it looked at hrst signt. In order that this might be made clear it was necessary to enquire rather fully into the nature of the germ-change referred .to, and it was here that divergence of opinion occurred. There were two chief views on the subject:?
(1) That the change was a defect mutation which could be inherited as a Mendelian recessive. This theory he regarded with the gravest doubt, and, although it was said by some to be established, he thought this was far from being the case.
(2) That the change consisted in a form of devitalisation arising^ as^ the result of certain adverse factors in the environment; as a consequence of this devitalisation the develop- mental capacity of the brain cells was diminished, and hence some degree of mental deficiency resulted. It was important to note, however, that the degree of germ impairment might vary in different generations and was not a fixed Mendelian unit. Moreover, the environ- ment (i.e., all external factors operating on the offspring from the time of fertilisation^ up to the period of completed development) must necessarily exert an influence on the reansa- tion of the innate potentiality. Hence it followed that in some members of the family the germinal change might remain latent, whilst in others it might be manifested, not neces- sarily as mental deficiency, but as epilepsy, mental instability, insanity,^ or dementia prajcox, etc. This view was enunciated by him 25 years ago, and his experience since that time had confirmed his belief that it best explained the majority of cases of mental defect.
Discussing, in the light of it, the question of the prevention of mental defect, it was, he continued, obvious that any measure which merely aimed at preventing the propagation of existing defectives could have but very limited results. The number of children born of parents who were themselves certifiable defectives was relatively small, and to produce any marked result it would be necessary to prevent the propagation of all those individuals who were carriers of the taint. This was not only impracticable, but impossible. Never- theless the prevention of propagation by defectives would undoubtedly have some result ^ in decreasing their number; hence we must take steps to that end either by their sterilisation or segregation. Of these he advocated the latter as the more practical and satisfactory policy for the country to adopt.
Meanwhile there remained the wider issue which lay at the root of the whole problem, viz., the prevention of tnat variation of the germ plasm which was the fundamental cause of the neuropathic diathesis. So long as this was considered to be due to mere chance,^ it was obvious that nothing could be done; but if he was correct in his view that the prime cause of germ deterioration lay in adverse conditions of the environment, then it to ‘ow.? that the outlook as to prevention at the very source was much more hopeful, and wit greater knowledge of these various adverse factors, the medical profession would be ab e to play a successful part in stamping them out. In this way not only would mental detect be lessened, but there would result a great improvement in the general health ot the com- munity.
Dr Tredgold concluded his paper by a consideration of the problem presented by secondary amentia, viz., that variety of defect which is produced by some adverse factor operating not upon the^ germ plasm, but directly upon the embryo or young child. Ihe prevention of this^ condition involved the prevention of the specific causes. Ihus, in cases due to vascular brain lesions occurring during birth it was probable that a better obstetric technique might save many children from becoming defective. In cases due to toxic or^ inflammatory brain lesions we needed more bacteriological research as to the organism which was responsible. More research was also needed into the cause of Mongolism, at present quite unknown to 12 MENTAL WELFARE. us, and the number of cases of which seemed to be increasing. Mental deficiency due to syphilis failed entirely to respond to treatment, and here the only possibility of prevention seemed to lie in the treatment of the mother before pregnancy. Dr Tredgold finally emphasised the fact that mental deficiency was a social problem of the utmost importance as well as a medical one, and that its prevention?closely related as it was to other forms of mental disorder and defective durability?was a matter of the most urgent necessity from the point of view of the further evolution of mankind. The application of the knowledge we already had would to a certain extent help towards this end, but on many points that knowledge was still very defective, and provision for scientific research would be greatly to the benefit of the nation and the race. In the discussion which foliowed Dr Tregold’s paper, various points were raised, and various views put forward.
Dr Robert Hutchison (London) dissented altogether from any theories of heredity, main- taining that there was no evidence for them, and that mental deficiency would always exist and was inevitable, with the exception of a few cases due to head injury at birth, which might be prevented. With regard to Mongolism he said that he had always found in his own experience that the mothers were over 35, so that it would seem that the only practical way to eliminate this condition was to prevent women over this age having children ! Dr Eric Pritchard (London) said that if the germ plasm could be injured by noxious influences?e.g., lead, mercury, etc.?and the influence continued through several genera- tions, it was only logical to suppose that if these adverse influences ceased, the inborn traits resulting from them could be bred out. He pointed out the part played by food accessory factors, particularly vitamin 13. starvation, which might be a potent cause of injury to the germ plasm. He also referred to a recent American suggestion that Mongolism was a primary and not a secondary form of mental defect.
Dr IV. A. Potts (Birmingham) advocated segregation as a means of prevention, but thought that certain other factors, such as toxic conditions during pregnancy, and too frequent pregnancies, should also be borne in mind in considering preventive measures. This point was emphasised, too, by Dr Bernard Myers (London). Dr Langdon-Down (London) expressed himself as in substantial agreement with Dr. Tredgold’s views.
Dr Crofton (Dublin) urged the importance of environment?a view which he said was shared by everyone who had studied its influence on the morphology of micro-organisms. Dr K. M. Marshall (Manchester) agreed with Dr Tredgold that the neuropathic diathesis was not inherited as a Mendelian recessive, but dissented from the view that mental deficiency was the culmination of a process beginning with a functional neurosis. Dr Lapage said that he considered there was no distinct gap between certifiable mental deficiency and the lower grades of those children who were not actually certifiable, and that both conditions were due not to hereditary change but to some alteration in the germ cell or embryo.
Dr H. B. Brackenbury (London), dissenting from this view, maintained that there was an absolute distinction between mental deficicncy and backwardness, even though their differen- tial diagnosis was difficult.
The President (Dr Leonard Findlay) regretted that the discussion had not resulted, as he had hoped, in the enunciating of an agreed and definite opinion on the subject. He doubted whether heredity could be considered as the chief cause of mental defect, and in his own experience in dealing with cases in the more educated classes family histories pointing to heredity were not found, nor did social status appear to make any difference in incidence. There was, he said, no concrete opinion regarding causation. The prevention of primary or congenital defect was the problem to be solved as the prevention of secondary or acquired form was merely a question of better medicine. But he doubted whether the large amount of money we were spending on the treatment of mental defect was ” worth while.”
Dr Tredgold, in replying, pointed out the difference between true mental defectives and the type of ineducable children found in some Special Schools, whom he said resembled the American ” morons.” He did not regard many of these latter as defectives within the mean- ing of the Mental Deficiency Act, but considered that they should really be classed with the ” dull and backward ” group. Legal mental deficiency, on the other hand, was a definite pathological condition. Dr Hutchison, he considered, was quite unjustified in throwing over- board all the valuable research work and data which has been accumulated regarding heredity, and he (Dr Tredgold) had no doubt that all those who had long and special experience of defectives would be in agreement as to the hereditary causation of this condition in the majority of cases. As to the President’s question, whether it was worth while to spend money on the treatment of defectives, he would ask what was the alternative ? Unless we were pre- pared to eliminate them by a lethal chamber or some such means, which was clearly impos- sible, then, obviously the general interests of the community demanded that we should make them as little dange’rous and as useful as possible. This could only be done by training adapted to the needs of the individual patient followed by proper supervision, and he con- sidered that there was abundant evidence that these measures had not only met with a considerable degree of success, but that they were economically sound. All those with experi- ence of defectives knew that in the long run it cost the State less to train and care for these persons than it did to neglect them.
Although it did not result in any agreed authoritative pronouncement, the debate should be of considerable value to all concerned in the care of defectiv es ?medically, educationally or administratively?in that it shows them what is the present state of expert knowledge as to the causation of mental defect. It should, moreover, serve to prevent them from falling into the popular erroi one all too rife in this particular problem?of making sweeping generalisations on a subject upon which there is as yet no consensus of opinion even amongst those who have made of it a life study.
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