Undoubtedly, a great portion of the mental and nervous disorder commonly attributed to heredity is largely caused or aggravated by imitation and by vicious training of children. Schopenhauer says that the normal man is two-thirds will and one-third intellect—in other words, two-thirds made by education and one-third by inheritance. The intellect is often trained so as to enfeeble the will as well as to hinder the development of the physical man. Self-culture may so degenerate into self-indulgence as to destroy individuality and force; and mental health, as a rule, depends upon bodily health and the exercise of self-control.
In the uncivilized and half-civilized races of the world insanity is rare; in the early civilizations the insane perished from neglect, were hanged and burned, starved and died in famine and pestilence, and fell among the foremost in war. Some of the tribes of North American Indians shoot the insane, considering them possessed of evil spirits, while their white neighbors keep them in chains and squalor. Civilization brings better food, clothing, and shelter, and less danger from war, famine, and pestilence than savage or mediæval times. In the struggle for existence, however, physical strength no longer wholly wins the day, but also those faculties that involve great mental and bodily strain in mines, factories, crowded tenements, counting-rooms, offices; in the eager, excited over-study for prizes or rank in overheated, badly-ventilated schools, and, indeed, in every walk of life. People with marked neuroses, who would have gone to the wall a couple of centuries ago from want of physical strength, now support themselves by indoor light work, marry, and reproduce their kind. Minute division of labor involves monotonous toil and increases the impairment of the body's resistance to mental and nervous strain, and abuse of the nerve-stimulants tea, coffee, tobacco, or, worst of all, alcohol and narcotics, add to the evil. Degeneration due to the reproduction of poor stock is intensified by intermarriage. Luxury, idleness, excesses, syphilis, debility, drunkenness, poverty, disease, and overwork produce vitiated constitutions in which varying types of insanity appear in various nations and climates, but, so far as is known at present, not in very different degree under similar conditions. One of the great problems of the day is whether the many conditions incompatible with health in our crowded populations can be overcome so as to prevent the degeneration going on thereby.
In early life chiefly the degenerative or the hereditary type of insanity occurs, or some modification of it. The prevalent forms coming next are insanity of puberty and adolescence and the curious morbid psychological developments of lying, stealing, running away from home, all sorts of perversity of action and thought—impulse overpowering reason; often resulting in cure if wisely treated, but not seldom ending in various forms of so-called moral insanity, suicide, epilepsy, hysteria, primary insanity, prostitution, and offences against the laws. It is largely a matter of accident rather than a result of any established principle whether such boys and girls are sent to reformatories and prisons or to insane asylums. In the progressively advancing years of life organic mental disease and the psychoneuroses are more common, the favorable or unfavorable type of which depends largely upon the degree of degenerative tendency in each case.
The exhaustion and the disturbed cerebral circulation arising from acute and chronic diseases, profound anæmia, or prolonged mental strain, associated with emotional disturbance from any cause, are among the antecedents of insanity. By our asylum reports ill-health is second only to intemperance as an exciting cause of insanity, and ill-health comes probably more largely from poverty than from any other direct cause. Diseases and accidents to the mother during gestation and injuries to the infant's head during parturition may reasonably be supposed to so affect the fœtal brain as to predispose to insanity in later life.
Of 18,422 admissions tabulated from reports of Massachusetts asylums, the prevalence of insanity by ages was approximately as follows:
| Age. | Number of Admissions. | Population by Census of 1875. | Admissions per 100,000 of Population. |
| 15 and under | 366 | 312,1036 | 117 |
| 15 to 20 | 1,380 | 165,936 | 832 |
| 20 to 30 | 5,269 | 310,861 | 1695 |
| 30 to 40 | 4,632 | 240,966 | 1922 |
| 40 to 50 | 3,372 | 182,823 | 1789 |
| 50 to 60 | 1,797 | 126,430 | 1421 |
| 60 to 70 | 976 | 79,186 | 1106 |
| 70 to 80 | 382 | 38,283 | 997 |
| Over 80 | 58 | 11,167 | 519 |
| Age not reported | 190 | 10,302 | |
| Total | 18,422 | 1,478,0576 | 1246 |
| Total of all ages | —— | 1,651,912 | 1115 |
6 Excluding those under five years of age.
Of the 36,762 persons of unsound mind known to the English lunacy commission in 1859, there were 31,782 paupers, or 86.45 per cent., as compared with 4980, or 13.55 per cent., supported by themselves or their relatives. At the close of 1880, of 73,113 insane, 65,372, or 89.41 per cent., were paupers, and 7741, or 10.59 per cent., were private patients or self-supporting. The increase in the number of the latter from 1859 to 1883 was from 2.53 to 2.96 per 10,000 of the population, or 17 per cent., and of the pauper insane from 16.14 to 25.72, or 59 per cent., while general pauperism had rapidly diminished from 43.7 to 29.5 per 1000 inhabitants.
Similarly, of 9541 admissions to the State hospitals for the insane in Massachusetts from 1871 to 1880 inclusive, there were 4166 State patients, 4050 supported by cities and towns, and 1325 private patients; in other words, 86 per cent. were supported by public charity. Of 7963 admissions in the same time in which the nationality was stated, 4532 were natives and 3431 foreigners, respectively 57 and 43 per cent., whereas by the census of 1875 the natives were 74.64 per cent. of the population, showing more than twice as great a percentage among foreigners (chiefly laborers) as among natives. It is quite clear, therefore, that insanity is more prevalent, or at least increasing more rapidly, among the lower parts of the social scale than higher up; but it is impossible to say how many people have dropped from higher planes of life to lower.
Although women are probably more predisposed to insanity than men, and men more exposed to its objective causes than women, it is not certain that more insanity occurs in either sex. It is somewhat more prevalent in single and widowed and divorced people than in those married. The period of greatest prevalence is earlier in women than in men.