External agents producing sudden terror have been frequently known to bring on insanity. It is related of a child of three years of age, who was so terrified on being brought into a madhouse, that he was subject to horrible dreams and visions until his seventeenth year, when he became a perfect lunatic. Women frightened during pregnancy have often become alienated; and there are two cases reported of young ladies who were found insane the day after their nuptials.
While disappointments and misfortunes are often the origin of insanity, a sudden melioration in circumstances, and unexpected pleasing intelligence have been also known to derange the intellects. A man who came into the possession of a large fortune, after having lived for many years in penury, was so alarmed at the thought of losing this property, that the apprehension of the evil deprived him of his senses. An instance is recorded of a young girl, long separated from her lover by parents averse to their union, who became insane immediately after her marriage.
Children are generally exempted from this calamitous visitation; yet Frank relates the case of a child at St. Luke’s who had been deranged since he was two years old. Age, to a certain extent, seems to influence insanity, and most individuals are alienated between their twentieth and fiftieth years. Haslam states, that out of one thousand six hundred and sixty-four patients admitted into Bedlam, nine hundred and ten came within this period of life. In France it appears that most cases of insanity are noticed between the ages of twenty-five and thirty-five. One-fifteenth of these cases among men, and one-sixth among women, are observed before their twentieth year; and in the wealthy classes of society one-fourth occur before the same period. The following table from Bicêtre regarding age is not without interest.
| Years. | Aged | 15 | 20 | 30 | 40 | 50 | 60 | Total. |
| 1784 | ... | 5 | 33 | 31 | 24 | 11 | 6 | 110 |
| 1785 | ... | 4 | 29 | 49 | 25 | 14 | 3 | 124 |
| 1786 | ... | 4 | 31 | 40 | 32 | 15 | 5 | 127 |
| 1787 | ... | 12 | 39 | 41 | 26 | 17 | 7 | 142 |
| 1788 | ... | 9 | 43 | 53 | 21 | 18 | 7 | 151 |
| 1789 | ... | 6 | 38 | 39 | 33 | 14 | 2 | 132 |
| 1790 | ... | 6 | 28 | 34 | 19 | 9 | 7 | 103 |
| 1791 | ... | 9 | 26 | 32 | 16 | 7 | 3 | 93 |
| 1792 | ... | 6 | 26 | 33 | 18 | 12 | 3 | 98 |
| 1793 | ... | 4 | 36 | 28 | 22 | 13 | 10 | 113 |
| Total | 65 | 329 | 380 | 236 | 130 | 53 | 1193 |
Thus it would appear that the astounding events which took place in France, but more especially in Paris, from the year 1789, the breaking out of the revolution, to 1793, the reign of terror, had no effect upon the intellects of the population; unless it is supposed that the entire nation being in a state of insanity, either madmen were not noticed as any peculiarity, or rushed into mischief and were murdered. This observation as to the influence of public events is confirmed by the following statement of admissions in the Salpétrière during the comparatively tranquil years of 1811, 1812, 1813, and 1814, although many cases of insanity were said to have arisen from the harsh laws of the conscription.
| Years. | Aged | 20 | 25 | 30 | 35 | 40 | 50 | 60 | 70 | 80 | Total. |
| 1811 | ... | 34 | 37 | 38 | 27 | 48 | 38 | 24 | 12 | 4 | 262 |
| 1812 | ... | 52 | 34 | 33 | 18 | 38 | 57 | 26 | 19 | 3 | 280 |
| 1813 | ... | 43 | 29 | 33 | 41 | 32 | 57 | 31 | 13 | 6 | 285 |
| 1814 | ... | 42 | 35 | 38 | 31 | 26 | 53 | 34 | 22 | 10 | 291 |
| Total | 171 | 135 | 142 | 117 | 144 | 205 | 115 | 66 | 23 | 1118 |
Therefore one might fairly conclude that the taking of the Bastille, the execution of Louis XVI., the bloody sway of the Jacobins, the ambitious wars of Napoleon, and the restoration of Louis XVIII., did not in the slightest degree affect the brains of our happy and philosophical neighbours.
It has been generally imagined that women are more subject to mental alienation than men; this, however, is by no means proved by observation in other countries, as will appear by the following calculation: