Nostalgia and homesickness are not currently regarded as mental disorders. The psychic pain associated with longing to return home had been considered a mental disorder for centuries, especially in Europe, where it was a sign of moral weakness between nations. Nostalgia's effects on American Civil War soldiers—anxiety, depression, and sleep and appetite disturbances, for example—were described by clinicians and linked to significant morbidity and mortality. Since then, although these effects of combat have been of interest, focus has shifted to psychic trauma, relegating the concept of nostalgia to an unclassified but commonly encountered condition. Besides wartime trauma, symptomatic conditions related to nostalgia have been described among displaced persons and refugees living in the diaspora longing for their homelands (e.g., social displacement syndrome). More recently, nostalgia has pervaded culture as a benign pastime, with no implications for psychopathology. Finally, the longing for return to an idyllic or imagined lifestyle has returned amid worldwide quarantining and isolation during the COVID-19 pandemic. In this new sense, nostalgia has become a remedy rather than a disease. We identify four major iterations of nostalgia: the medical condition of homesickness, the condition studied in wartime, the application to migration and social displacement, and as a remedy for existential anxiety. We conclude that nostalgia per se is neither pathological nor normative, but a consistent phenomenon in human existence that should not be overlooked in cultural assessment and psychotherapy.