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The Causes Of Nervousness (Heredity)

( Originally Published 1908 )

As the phenomena of nervousness are so general in character we may well suspect its causes to be likewise general. In fact in so far as nervousness is an affection of personality we may look for its causes in all the influences which affect our personality. Modern science has reduced these to two general categories, heredity and environment, and no less comprehensive complex of causality will account for the well-nigh universal nervousness which pervades our modem world. So far as I am aware the history of nervousness has not been written, but it would be a mistake to suppose that nervousness was unknown to the ancient world. Where insanity and suicide have prevailed we may be sure that the milder functional disorders were not absent. To cite a single example, no secondary personalities have impressed themselves more deeply upon the pages of the New Testa-ment than the sad figures of the demoniacs, the paralytics, the epileptics, and the maniacs whom Jesus so frequently encountered. The Jews, with their wonderful excess of, vital power, suffer much from nervous irritability at the present time and with them this is no new disease. The New Testament reveals the wide-spread neurotic conditions which prevailed at the time of Christ, and from all we know of the moral life of the pagan world at the beginning of the Christian Era it is plain that Graeco-Roman society was even more deeply affected. Antiquity, however, knew not syphilis.

While reading the description of the various neuroses just given, it must have occurred to more than one person to ask, whence come these strange affections of personality? Functional nervousness is not a disease of invasion like diphtheria or tuberculosis due to the presence in the system of pathogenic microbes. It is not a malady caused by the lesion or degeneration of vital organs. Whence then come these sad moods, these morbid states of mind, this melancholy, this irritable weakness, these unseasonable fears and sad transformations of character. These are questions which the physician who deals with such disorders has to face every day, and in fulfilling his calling his first inquiry is usually as to the family history of the patient. In other words, in all serious nervous disorders heredity plays a very important part. We have been so greatly cheered during the past few years with the good news that tuberculosis is not an inherited disease that a good many persons have encouraged themselves with the thought that this may also be true of all other maladies, but it is not true of nervous diseases whether they are functional or organic. As nervousness in all its forms is a very general condition, rooted in constitution and temperament, the conditions which lead to it are the more likely to be transmitted. Moreau of Tours tells a sad story of the times of the French Revolution. In 1789, a man, terrified by the first revolutionary excesses, shut himself up in his room which thenceforth he refused to leave for a period of ten years. When his daughter reached the age at which her father had incarcerated him-self, she followed his example although the Revolution was then over, and remained a prisoner for the remainder of her life. This recital strikingly shows us how nervous conditions in parents repeat themselves in children, frequently in a severer form. Dr. George Carroll Smith, of Boston, in a recent paper analyzes the history of one hundred neurasthenic cases taken at random from his own practice, and of these he finds forty-three "clearly hereditary" and fifty-seven "acquired." This proportion is probably not unusual, although it is to be remembered that nervous affections are transmitted far more frequently than is true mental disease. This is true of epilepsy, hysteria, neurasthenia, and neuralgia, alcohol-ism, a morbid impulse to _suicide, certain criminal tendencies, migraine, chorea, developing in late adult life, muscular wasting and peculiar forms of spinal cord disease. It does not always happen, however, that these tendencies reappear in children in the exact form in which they appeared in the parents. On the contrary, these affections, like insanity, are frequently transformed in transmission. But when in one and the same family we find a constant tendency toward nervous disorders appearing now in the form of insanity, now as epilepsy, now as hysteria, or again as alcoholism, neurasthenia, or imbecility, it is necessary to suppose some constant and general cause.' Nor need the variety of these affections cause us any surprise when we remember how readily one nervous condition passes into another and how constantly their symptoms run together. Frequently the recurrence is delayed. The child may be healthy and he may grow to a fine and vigorous man, but at last the fatal hour may strike that summons him to follow the way of his fathers. I have in mind a family in which the father after leading an exemplary life for forty years suddenly developed a craving for alcohol which lasted for nearly twenty years when he entirely ceased drinking. Four fine sons, the two elder born before their father's downfall, have followed in his footsteps. In them all the morbid craving developed comparatively late, after thirty. But whereas the father reformed and is still alive, two of his sons drank themselves to death, one is paralyzed, while the fourth has completely disappeared. This illustrates one of the most pathetic aspects of the transmission of nervous ills. Disorders which were only temporary in parents are frequently permanent in children. As M÷bius puts it, a passing delirium in a parent may establish inextinguishable marks of degeneration in offspring.' As we ascend the course of a degenerate family we usually come to a point beyond which health prevails. In other words, we can trace the inherited disease directly to some ancestor near or remote with whom it began. Morel gives such an example in the history of a family in which the great-grandfather was a drunkard and died in consequence of excessive indulgence. His son who was also an inebriate died insane, the grandson though temperate was a hypochondriac with murderous instincts. The great-grandchild was weak-minded and idiotic and with him the succession fortunately ceased. Terribly significant is the appended chart of Dr. Doutrebente in which it is shown how the sickness of the father reappeared in the most manifold forms through two generations, with the result that a numerous family was extinguished in the third generation.

On the other hand it ought to be remembered that by no means all the children of nervously diseased parents inherit a diseased nervous system. Some are perfectly healthy, some even in degenerate families are men of genius. Frequently the defects of one parent are offset and almost nullified by the excellence of the other. Hence the results are apt to be far more serious when both parents are nervously affected. Again, when undesirable and even dangerous tendencies are plainly present in children their development can often be checked by a wise training and. by a wholesome mode of life. Man is not merely the victim of fate, the product of hereditary influences over which he has no control, he is also a moral being endowed with a will which in innumerable splendid instances has resisted destructive tendencies and vanquished them. Environment also counts for much. In general the probability of transmission, and the severity of the transmitted disease, depends upon the severity of the disease or degeneration in the parents. (M˘bius.) Yet it frequently happens especially in mental diseases that the malady is not propagated directly from father to son. Very often the affection appears in one generation in the aunt or uncle, and the next in the nephew or niece, or the disease may skip one or more generations and reappear in a subsequent one. This shows once more how exceedingly general and diffuse nervous disorders are apt to be. In the former case (aunt or uncle) it is necessary to ascend higher to find the origin of the disease.

One of the causes of inherited nervous diseases is inter-marriage. When a morbid taint appears in a family it can be checked and eventually extinguished by the constant infusion of fresh and healthy blood. But when near relatives marry, both of whom carry within them the same morbid germs, the obvious result is accentuation of the family weakness. Royal and noble families among which intermarriages are frequent are constantly threatened with degeneration, insanity and extinction through the operation of this law. (Niebuhr, Esquirol, Spurzheim, Quatrefrages, Mains.) The Jews alone seem to be unaffected by consanguineous marriage. Incompatibility between parents, lack of sympathy and affection, are also unfavorable to the production of sound and vigorous offspring. On this subject Schopenhauer's observations 1 are very interesting. Children sprung from such unions, he affirms, are apt to be sad and inharmonious beings.

These, however, are secondary causes. They teach us the solemn lesson that diseased nervous conditions are transmitted, but they cannot tell us how such conditions are acquired, or how nervousness came into the world. To learn this lesson we must turn to the life history of the individual and trace the effect of environment upon the nervous system, but before we do this it is well to remind ourselves once more of the effect of our acts and states upon our children. In the moral world the law of causation prevails with the same inexorable certainty that characterizes its action in the physical world. Nervous and moral conditions are transmitted and they frequently become graver in the process of time. The severest and most incurable forms of nervous disease are usually those which are attended by a bad family history. Many families bear in the persons of the majority of their members the stigmata of moral and physical degeneracy. From this point of view, the ancient doctrine that the sins of the fathers are visited on the children unto the third and fourth generation is true to the letter, for in the third or fourth generation such heavily burdened families almost invariably are extinguished. Nature, which apparently hates abnormality, sees to it that the abnormal and the degenerate do not propagate their degeneracy indefinitely upon this earth. We shall see, however, that by no' means all nervous disorders are the result of moral delinquency. Many of them are imposed upon us by conditions of life over which we have practically no control.

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