By the modern alienist, the influence of the menstrual reflex on mental affections is recognized only in cases in which a proper valuation of the predisposing causes has been made, in such cases as the following: First, we have to recognize the modifying influence exercised by the menstrual stimulus on established psychoses, inasmuch as these latter not infrequently undergo cure when previously irregular menstruation has become regular, and, moreover, the recurrence or the first appearance of menstruation has often a powerful influence on the course of some established mental disorder. In some cases this influence is a strikingly favorable one on psychoses that have developed before the commencement of menstruation, or during the suppression of that function; it may be, however, and, indeed, more frequently is, an unfavorable influence, inasmuch as such a psychosis, on the first appearance or on the reappearance of menstruation, may assume a menstrual type, the attacks becoming more frequent or more violent with the successive recurrence of each menstrual or premenstrual period. This is the history of the typical menstrual psychosis.
Again, certain processes of the sexual life, disorders of menstruation, diseases of the genital organs, operations on these organs, and the processes of the climacteric, influence the origin and the character of mental disorder, generally giving rise to chronic affective insanity (insanity of the emotions and feelings) or to paranoia (chronic delusional insanity, insanity of the intellect). The menstrual stimulus must in these cases be regarded as a psychopathically exciting physical cause.
Further, physical disturbances may equally affect the menstrual function and the functions of the mind, rendering the exact causal sequence in such cases a difficult one to determine; and, conversely, the circumstances that restore the normal working of the mind may also regulate the menstrual function.
Finally, we may have to do with isolated sporadic occurrences in which the exciting influence of menstrual processes may be traced. Thus, for the outbreak of a periodical menstrual psychosis, an especial temporal predisposition must exist, connected with the great developmental epoch of the sexual life.