The causes of insanity include all of the numerous causes to which attention has been called in the first part of this section, as productive of nervous disease. Anything which tends to interfere with the nutrition of the brain may become a cause of insanity.

Among the special causes, may be mentioned excessive mental exertion, powerful emotions, unrestrained passions, sexual excesses, disorders of the digestion, the use of opium, alcohol, and tobacco, general disorders of the system, disease of the kidneys, liver, and other internal organs, organic disease of the brain, spinal cord, etc. One form of insanity makes its appearance during pregnancy, or after childbirth. It seems to be dependent upon this particular condition. Religion has been charged with producing insanity in persons who have given themselves up to religious exercises in an immoderate degree, but we seriously doubt whether genuine religion is in any case the real cause of mental disease. Religious fanaticism may lead to insanity, if, indeed, it may not be considered one form of mental disease. We have found by careful investigation of a number of cases of so-called religious insanity, that some other cause really lay at the foundation of the disorder, as unrequited affections, disappointment in love, or some other condition in which the emotions were strongly involved; loss of sleep; long standing nervous disease, etc.

In not a few instances, we have found the real cause of so-called religious insanity to be self-abuse; indeed, we are thoroughly satisfied that sexual excesses are responsible for a much larger proportion of mental disease than is generally supposed to be the case. Heredity is also a very common cause. It has long been thoroughly established that a tendency to insanity runs in families. The children of epileptics are likely to be insane. The notable increase of insanity is one of the most alarming features of the times. At the present time there are more than forty thousand lunatics, recognized as such, in the United States, while there is, undoubtedly, a much larger number of individuals who are suffering with a moderate degree of mental disorder, but have thus far been able to escape detection.