The objective of my study has been to investigate the linkages between the production of some writers from the late 18thto early 19thcenturies and the psychological school of that period, focussing on how scientific thought has developed the concepts of well-being, illness, therapy, psychic anomalies, normality, neurosis and madness. Special emphasis has been placed on the ways by which such elements have influenced biography, and especially on the creative extent by certain authors of the ItalianScapigliatura, Verism and Decadence. I have made an attempt to delve into the scientific knowledge of that period with regard to mental illnesses such as hysteria, dual personality, obsessive behaviours, volition disorders and paranoia, as well as to document the influence, either demonstrated or highly likely, of such doctrines on the fictional production by Tarchetti, Serao, Fogazzaro, Capuana, De Roberto, D’Annunzio and Pirandello. I have tried to demonstrate that in the main characters of the novels by Tarchetti and Serao description of the illness does not match a rigorous scientific documentation; whereas the portrait of the alienated characters by Capuana, Fogazzaro, De Roberto, D’Annunzio and Pirandello relies upon carefully considered and often certifiable scientific tenets within the Physiology, Psychology and Psychiatry of that period.