A Treatise on the Incubus, or Night-Mare, Disturbed Sleep, Terrific Dreams and Nocturnal Visions

by John Augustine Waller

It sometimes appears in very early life, in which case it generally sticks close to the patient, almost all his days. In some, however, such a change in the constitution takes place at puberty as destroys altogether that predisposition to this affection, which existed in early life.

Females appear much less subject to it, than males, though by no means exempt. Of these, virgins and pregnant women are more particularly liable to its attacks, as well as all those who are much visited by hysterical affections, constipation, and flatulency. It is sometimes also found to accompany the chlorosis or green sickness. On the whole, however, it is of comparatively rare occurrence amongst females.

Neither is this disease very common in advanced life, unless where corpulency, or a tendency to lethargy exists. In those cases however where it does occur, it is more to be dreaded than in youth or middle age. It is no unfrequent attendant on asthmatic persons.

The opinions of medical men with respect to the immediate cause of this disease, or what by them is termed its proximate cause, have been various and discordant, as generally happens in all obscure investigations. In all probability every one of them are wrong, so that it can be of little utility to inquire into them. There is however one idea, which seems to be more universally adopted than any other, and which deserves notice; it is, that this affection is produced by a cause purely mechanical, and depending on the position of the body. Some plausible theories have been formed on this supposition, by assigning to the different thoracic and abdominal viscera, certain relative positions which would occasion a temporary pressure upon the organs of respiration, or upon some branch of the intercostal nerves. With respect to this mechanical pressure, arising from any imagined position of the patient, what I have already said on that score, renders this hypothesis vain, for there is no position in which it is possible for a person to fall asleep, in which I have not been attacked by Night-Mare. Neither is there any more dependence to be placed on the generally received opinion, of the disease being induced by a full stomach. It may naturally be supposed, that any person labouring under this affection to the degree which I have stated, although I have as yet given a very feeble idea of its extent, would take every possible precaution to keep clear of the causes, which were so generally believed to have produced it. I religiously abstained, for many years from eating any thing after dinner, and took dinner also at as early an hour as two o’clock. It was during this period that I suffered most from the disease. I think I may safely assert, that for more than twenty years, I have never once, to the best of my recollection, fallen asleep on my back, or ever found myself in that position on waking. When night after night has been rendered miserable by this enemy of repose, I have had recourse to every expedient which deep reflection could suggest. The perpendicular position of the body, I have found by experience to be the worst in which a paroxysm of Night-Mare can be borne. The difficulty of respiration, and all the other symptoms are greatly aggravated, and an additional one is felt, which greatly increases the sufferings of the patient; it is a perpetual dread of falling, which appears inevitable, and which prevents the patient from struggling so much as he would do if in a horizontal position. Next to this is the position of sleeping with the body bent forwards, and the head reclining with the face downwards on a table: in this last position, the difficulty of inflating the lungs is extreme. I have never been able to discover that any great difference arose between sleeping on the right or left side. I have always considered it as a matter of indifference. Although it is possible to render the paroxysm of Night-Mare more tolerable by any particular position of the body, yet I am well assured that no position will secure a person from its attacks, to whom it has once become habitual. I slept for some time in an easy chair, and found the disease greatly aggravated by it.

There must however be some reason for the universal opinion that it always attacks persons lying on the back. I was for a long time of opinion myself, that I was always lying in that position when the paroxysm came on, but as the disease gained strength, and the paroxysms hung more pertinaciously upon me, I became more perfectly awake, so as to be able to discover more accurately the position in which I was lying, and I found that little faith was to be given to the sensations that may occur during Night-Mare, as they are the most deceitful of all evidences. It appears to be one of the symptoms almost inseparable from the disease, that the patient should appear to himself to be kept down upon the back by some external force. This sensation I have almost always felt, even when I have had the evidence of other people, as well as my own conviction when awake, that I was in reality lying on the side. I cannot help suspecting that many others have been deceived in a similar manner, and thus made to believe, that they never had the Night-Mare except when sleeping on their backs. There is also another sensation which is very apt to deceive the patient, that is, on the paroxysm going off, and the moment of his recovering the power of volition, a great confusion of ideas always takes place, and a person to whom the Night-Mare is not very familiar, generally imagines that he has recovered himself by some effort of his own, frequently by turning from his back to his side, sometimes by sitting upright in bed. These things are all extremely fallacious; there is no trusting to the senses during a paroxysm of Incubus; nothing short of the evidence of another person ought to satisfy the patient. I have often been thoroughly convinced in my own mind that I had succeeded in throwing the bed-clothes off my breast, and by that means gained relief, and not unfrequently, that I had risen from bed, and opened the window to admit air; yet both these ideas have been proved to be incorrect. I have often felt very certain that my right arm was out of bed, and that I had moved it about; but on waking thoroughly, I have found it under the bed-clothes, and in a situation in which it could not have been moved. I cannot help thinking then, that the universal idea of its attacking persons exclusively lying on the back, is founded on an error, arising out of the ordinary sensations of the patients themselves, who have always that idea, let them be in what position they will. Several persons, subject to habitual Night-Mare, have become convinced of the truth of this observation, which I had made to them, after attending more closely to their real situation during the continuance of, and immediately after the paroxysm. I have also convinced one or two medical friends, who were extremely sceptical on that point, that it would attack me in any position, by going to sleep before them, on a chair, or sofa, when my own feelings have indicated the certainty of attack, if I should indulge for a few moments the propensity I felt to sleep.

Neither is it necessary for the stomach to be filled with food, in order to produce Night-Mare, as is evident from what I have stated above with respect to the abstinence I observed during the period in which I suffered most from this affection. Experience has taught me that I may eat heartily of some kinds of food, just before going to bed, with impunity; whilst the smallest quantity of some other will inevitably bring on the disease, in spite of all the precautions that can be taken.

Thus then we must give up every explanation of the phenomena which occur in this disease, founded upon principles purely mechanical, however plausible they may appear. Neither is the opinion of Darwin more correct, that the Night-Mare is nothing more than a consciousness of the suspension of the power of volition, and a desire to recover that power. If so, it would differ little from sleep itself; or, however fatiguing it might be to the mind, it could not occasion any derangement in the functions. The breathing and the circulation would go on without any interruption, as in sleep; nor would there be any thing that could produce the sense of oppression on the breast. Darwin was well aware of this difficulty, and therefore chose rather to contradict the generally received opinion of oppression and difficulty of respiration. There is no doubt whatever of the difficulty of breathing, which any one may assure himself of, if he could have the opportunity of seeing a patient during the paroxysm of Night-Mare. I have taken considerable pains to assure myself of this circumstance from the evidence of other persons.

I must confess I have not hitherto been able to find any satisfactory explanation of the phenomena which take place during Night-Mare. The following observations which I have been able to make on the paroxysm itself, and on the more immediate causes which give rise to it, may possibly direct some happier genius to a more correct idea of its nature.

1st. I have frequently experienced that this affection may occur in very profound sleep, without breaking or disturbing that sleep, any farther than to produce a dream, the memory of which will remain after waking, in the same manner as that of any other impressive dream. Thus I have frequently dreamed that I had Night-Mare; supposing myself to be in a place, and under circumstances very different to those in which I really was. Under these circumstances I have never become conscious of the real situation in which I was, but on waking, remembered very well that I had been dreaming of labouring under Night-Mare. From this circumstance I conclude, that the Night-Mare is not, as Dr. Darwin insinuates, a state of imperfect sleep, but an absolute disease, which may occur, and go through its regular stages, whilst the patient continues to be, to all intents and purposes, in a natural sleep. There is no doubt but the disease, in this case, is much slighter than ordinary, although the impression made upon the mind may be very strong.

2nd. It happens still more frequently, that the patient is in a state apparently between sleeping and waking, when the paroxysm takes place; which has given rise to the belief, in many persons, that it came on while awake. I have often heard it described by others, (and have felt it myself) as a sense of weight, first upon the feet, and progressively advancing towards the breast, until the paroxysm becomes complete. In the beginning of this state of things, it appears to the patient that he might easily, if he would, move himself, and shake off the incumbent weight. He does not feel at all aware at that moment, of the suspension of the power of volition; nor does he feel any inconvenience from that circumstance until he begins to experience a necessity of exerting that power, in order to carry on the function of respiration. It is not until the involuntary action of the muscles concerned in respiration, in some measure ceases, that the patient perceives that he is absolutely labouring under Night-Mare.