The New Zealand official Year-book tells us that the proportion which the inmates of the lunatic asylums of the colony, and those out on trial, bear to the whole population changed from 1 in every 383 of population in the year 1884 to 1 in every 288 in 1900, this being equivalent to an increase, relative to the whole population, of about 33 per cent. in sixteen years. The change was regular and continuous from year to year, and was not confined merely to the period just referred to.
On the strength of these and similar figures alarmist articles on the great increase of insanity frequently appear in our newspapers and magazines, and the greater strain of modern competition and the unhealthy conditions of city life are generally assigned as the chief causes. But others doubt the reality of so great an increase in insanity, and these suggest that the large number of good asylums, with the greater use made of those institutions, consequent upon the increased consideration shown for those suspected of insanity, may be responsible for much or all of the apparent increase, whilst the inclusion of a greater number of mental maladies under the head of “insanity” may still further tend to swell the numbers which so affright us. In any case, it appears generally accepted that, without these or similar explanations, the statistics of insanity indicate a continued increase in the modern man of liability to that mental disorder.
Now, I propose to show that the statistics of New Zealand do not indicate any real increase in liability to insanity, even if the numbers returned be taken as the proper measure of the amount of insanity in the colony. For this purpose I shall take the yearly admissions into the various lunatic asylums of the colony. As these will be classified according to age, it is necessary to leave out of consideration the small number of patients of age unknown, but this will not appreciably vitiate the results. The statistics must also be taken as given in the annual volumes of statistics issued by the Government—that is, with the idiotic included amongst the insane. The number
of the former class, however, bears but a comparatively small ratio to that of the latter.
Table I. represents the results obtained in the manner described in the introduction.
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|65 and over||15.7||15.7||18.5||19.5||10.2||10.8||12.0||12.8|
The results given in this table for the first and last of the four periods considered are illustrated graphically in Plate II.
Comparing generally the figures given in this table for the two sexes, it appears that there is little difference for the sexes for ages up to 55 years, but after that the tendency to insanity is markedly greater in males than in females.
With respect to the males, it may further be noted that there was actually, during the whole period, a diminution in the number of patients supplied for each 10,000 of population for all ages up to 65; only for ages 65 and over is there an increase, and this is from 15.7 to 19.5. Further, during the years 1879–83 there were 1,207 male patients of known age received into the various asylums, and during the years 1894–98 the number was 1,508; but, if the populations of the various age-periods had supplied patients in the latter period in the same proportion to their numbers as in the former, the number of admissions from 1894 to 1898 would have been as many as 1,771. Thus the statistics, if they fairly correctly represent the amount of insanity, indicate an undoubted substantial diminution in the chance of insanity for the average male.
In the case of females there was, during the period considered, a diminution in the number of fresh cases of insanity relative to the population for all ages up to 45; in the three
age-periods above this age, however, there was an increase. But the earlier age-periods supply so few patients that it is not apparent from these facts alone whether on the whole there was a true increase or decrease of insanity amongst females. We find, however, that during the years 1879–83 there were 739 female patients of known age received into the various asylums, and during the years 1894–98 the number was 1,095; but, if the populations of the various age-periods had supplied patients in the latter period in the same proportion to their numbers as in the former period, the number of admissions from 1894 to 1898 would have been as many as 1,230. Thus we get with respect to females a result, as far as the figures are concerned, like to that we formerly obtained for males—namely, an undoubted falling-off in liability to insanity. The same result thus follows for the population as a whole.
To what degree of correctness the statistics represent the actual state of things is another question, into which I do not propose to enter; but the concern about the increase of insanity, which inspires so many articles, is founded on the figures as roughly put in statistical works, and I have shown that these figures, properly interpreted, afford no justification whatever for the inference usually deduced from them, but rather indicate a strong tendency in the direction of growing sanity.
If the reasons usually assigned to explain the commonly supposed increase in the tendency to insanity have really any force, if many are now classed as insane that would not have been so classed some years ago, and if many are now placed in institutions for the care of the insane that some time since would not have been so provided for, then there must indeed have been in recent years a very real and very marked diminution in the liability of the New-Zealander to insanity, in spite of modern competition and the disadvantages of city life. In fact, explanations are now wanted to account for statistics indicating a falling-off, and not a growth, in the tendency of the race to insanity.
Thus far we have considered only the yearly contribution of the colony to the total insane population, and it may not be yet quite clear how it is that the total insane population is increasing so much more rapidly than the population as a whole. The explanation lies in the great changes taking place in the age - distribution of the people, which has been fully explained in the paper already referred to.
Table I. shows that there is no great liability to insanity till about the age of 25, whilst after that age there is no very great change in this liability; indeed, the number of insane
persons under the age of 15 might, for most purposes, be entirely neglected. Now, whereas the total population of the colony increased between 1881 and 1896 by 43.8 per cent., the population in some of the later age-periods considered as much as trebled. Further, the number of people that become insane in any age-period during any year, as represented in Table I., does not represent the number actually insane in that age-period, for that number includes the survivors of all those belonging to that age-period who became insane in previous years and failed to recover. Thus the number of insane in any section of the people is cumulative relatively to the population, and the number of insane per 10,000 of the population must increase rapidly in the age-periods of maturity as we rise from one age-period to a higher one. This is quite distinct from the liability of sane persons at those ages to develope insanity, and, with the rapidly increasing proportion of the whole population included in the later age-periods, completely explains the continually growing proportion of the population that are afflicted with insanity. Considerations brought forward in the paper already referred to, leading us to expect a continued rapid increase for many years to come in the proportion that the old bear to the whole population, also lead us to expect a similar increase with respect to the insane, and this without the aid of any increased liability of the race to insanity, and possibly even in spite of a falling-off in such liability.