A psychological disorder exhibited by New York Yankee fans after the Yankees collapse in monumental fashion to the Boston Red Sox. Symptoms include denial, disparaging of the victorious team, contortions of the facial muscles into scowls, and sulking. Pakistani graduate students are particularly severely affected. Symptoms can be enhanced by the wearing of bandanas and Derek Jeter jerseys. Treatments for Haideritis generally include an admission of the inferiority of the Yankees and indeed of one’s own existence. The origin of the term Haideritis is commonly accepted as evolving from ‘hater-itis’, though the term has its true roots in the animal kingdom, as the actions of those suffering from Haideritis resemble those of the rodent Najamus Haiderus.
Some sketchy characters in the Frist Campus Center appeared to be afflicted with Haideritis when the Yankees lost the ALCS to the Red Sox in 2004.