The present paper examined the acceptance of psychological theories in the writing of Akutagawa Ryunosuke. The arrival of psychological science in Japan is linked to the work of Motora Yujiro in the Meiji period and, much like Fechner and Wundt, he was initially concerned with the analysis of physical reactions to external stimuli. With the advent of the Taisho period, applied psychology came to influence a range of fields, including education, medicine, law, and manufacturing, while at the same time Freudian psychoanalysis was gradually gaining attention. Perhaps because of such developments, Akutagawa’s depictions of madness may have borne some relation to these coinciding trends in psychology. The present paper analyzed Akutagawa’s descriptions of madness in the novels Loyalty(Chūgi, 1917) and A Bizarre Reunion(Kikai na saikai, 1921), written early and midway through Akutagawa’s career, respectively. In Loyalty, the trigger for the main character’s descent into madness is an external stimulus, consistent with the theories of Wundt, while the Freudian concept of repression is the cause of madness in A Bizarre Reunion. Akutagawa’s depictions of madness were thus transformed by the writer’s progressive adoption of contemporaneous trends within the field of psychology.