followed by a mental upset it is not apt to be overlooked by relatives or friends, but is rather likely to be mentioned as a cause even when an etiological relationship is not readily to be established. On the other hand, when an unfavorable environment insidiously undermines a subject's power of adjustment and thus gradually, without sudden catastrophe, leads to the development of a psychosis its significance is seldom fully appreciated, so that in histories furnished by lay informants, as they generally are, no cause is assigned.

Race.

§ 3. OTHER ETIOLOGICAL FACTORS.

An excellent opportunity of investigating the influence of race on the occurrence of mental disorders is afforded by the experience of the hospitals for the insane serving the city of New York, where people of various races are living under approximately similar conditions. This opportunity has been well utilized in a study by Kirby.1 Table 2, compiled from the figures furnished in that study, shows the relative frequency of certain psychoses in people of different races, given in figures representing percentages of the total number of admissions for each race to the Manhattan State Hospital, on Ward's Island, during the year ending September 30, 1908. It will be observed that the Irish are most liable to alcoholic psychoses, while the Jews are practically free from them; the latter, on the other hand, suffer most from the constitutional psychoses,

1 Geo. H. Kirby. A Study in Race Psychopathology. N. Y. State Hosp. Bulletin, N. S., Vol. I, 1909, p. 663.

especially dementia præcox and manic-depressive psychoses. The negroes are most liable to general

General paresis is said to be rare in Arabs and African negroes, although syphilis is common. This, however, is hardly more than a mere impression, satisfactory statistical data pertaining to this subject being as yet not available.

Age. All ages do not equally predispose to mental disorders. In general it appears that the incidence of the psychoses, as indicated by state hospital admissions, increases sharply with advancing age. This is shown in Table 3, which is based on statistics of population given in the Thirteenth Census of the United States and on those of hospital admissions furnished by the New York State Hospital Commission.1

The ages of greatest susceptibility are not the same

1 Twenty-third Annual Report, Albany, N. Y., 1912.

for all psychoses. Senile dementia seldom if ever occurs before the age of 60. Similarly, involutional melancholia is rarely seen before the age of 40. More than half of all cases of general paresis are seen between the ages of 35 and 50. The onset of more than half of all cases of dementia præcox and manicdepressive psychoses is before the age of 30. More detailed considerations of age are given in the chapters devoted to the various psychoses.

Sex.

* Including those of unknown age.

Mental disorders are more frequent in the male than in the female sex. Thus an enumeration of patients in institutions for the insane made on January 1, 1910, showed for the entire United States an average of 208.5 men and only 199.6 women per 100,000 of the general population. An even greater

contrast was presented by the admissions to the institutions during the year 1910, which were 72.1 men and 59.7 women per 100,000 of the general population. This difference seems to be due entirely to the greater frequency of general paresis and of alcoholic psychoses among men, the admissions for all psychoses other than these being about the same for the two sexes, averaging 54.4 men and 55.6 women per 100,000 of the general population.1

Environment. Statistics show almost invariably that urban populations contribute relatively much greater numbers of admissions to institutions for the insane than do rural ones. Thus during the year 1910 the urban population of the United States contributed 102.8 admissions, and the rural population but 41.4 per 100,000.1 This difference can be partly accounted for by the greater prevalence of alcoholism and syphilis in urban populations. Another factor having a bearing here is the difference between the two portions of the population in age distribution: only 27.2% of the urban population and as many as 36.3% of the rural population were under 15 years of age; we have already shown that the population groups under 15 years of age contribute but a very minute proportion of admissions to institutions for the insane.

For the rest, it seems probable that the difference

1 Insane and Feeble-Minded in Institutions. Bureau of the Census, Washington, 1914.

2 The expression "urban population" is here used, as in the U. S. Census, to designate all that part of the population which resides in cities, towns, or other incorporated places of 2500 inhabitants or more.

between urban and rural populations, as shown in statistics, is due not to a corresponding difference in incidence of mental disorders but to purely extraneous conditions, especially accessibility of institutions.1

Occupation. It is hardly to be doubted that occupation has an influence on the incidence of mental disorders, although satisfactory statistics pertaining to this matter are not available. Bartenders, brewery and distillery employees, and hotel waiters are more liable than most others to alcoholic psychoses; soldiers, sailors, traveling salesmen, and railroad employees are more liable to general paresis. Physicians, engineers, architects, clergymen, and lawyers would probably show a relatively low incidence of the graver constitutional psychoses.

Marital condition. Of all patients admitted to the institutions for the insane in the United States during the year 1910, 48.4% among men and 33.4% among women were single. In the adult population at large only 38.7% of the men and 29.7% of the women were single, — this in spite of the fact that the average age of patients admitted is higher than that of the general adult population (over 15 years of age) and that, on that score, the percentage of single persons should be less and not greater among the hospital admissions. This, however, "is not to be interpreted as indicating that the single are more liable to become insane than the married. It means

1 A. J. Rosanoff. A Study of Eugenic Forces. Amer. Journ.

of Insanity, Vol. LXXII, 1915.