Hofer defined nostalgia as a mental illness, citing cases in which people suffering from chronic nostalgia would fall into deep depressions. They would be consumed with sadness, apathy, and suffer from an inability to conform to or accept the customs of their new home. Because Hofer studied mostly Swiss subjects, it became known as the Swiss Illness.
There are records of the as-yet-unnamed nostalgia appearing before Hofer’s studies; during the Thirty Years’ War, Spanish soldiers were discharged from service because they suffered so strongly from it that they were no longer capable of fighting. In the early 1700s, Russian troops could be expected to be buried alive if they succumbed to the so-called nostalgia virus. And during the United States’ Civil War, soldiers who grew nostalgic for their homes and families were publicly shamed and ridiculed until they got over it.
In the 19th century, physicians were still searching for a physical source of nostalgia. The definition of nostalgia as a mental disorder lasted into the 20th century, when it was called the “immigrant psychosis.”