Insomnia reduced to simplest terms is nothing but the inability to sleep. While the causes of insomnia may sometimes be exceedingly complex, ordinarily they are evident both to us and those we love the best. Anything, as we all learn by experience, which accelerates the activity of the mind and increases the congestion of the brain is likely to induce insomnia. Worry, fear, grief, prolonged mental effort, any sort of emotional excitement, social dissipation, the intemperate use of coffee, tea, or alcohol are among the most familiar causes of insomnia. Disturbances of digestion, neuralgic pains, arterial disease, eye-strain, and dental lesions are the hidden causes, oftener than we imagine, of protracted wakefulness.

Many of the more obstinate cases of insomnia are due, we know at last through Dr. Upson’s remarkable book,6 to some dental lesion unsuspected because, as is not uncommon, it is unaccompanied by the ache habitually associated with all the ills to which the teeth are heirs. In my Emmanuel clinic I have had one case of insomnia which, in spite of all an efficient doctor could do for the body and the Emmanuel worker for the mind, persisted until I at last discovered that the sufferer was in immediate need of a dentist, whose threshold, through a morbid fear, he had not crossed in many years.