"The thing I fear most is fear," wrote the sixteenth century philosophical essayist Michel de Montaigne. He might have been referring to anxiety sensitivity, a phenomenon first described by psychologists in the 1980s and since then increasingly used in the explanation and treatment of psychiatric disorders.
Anxiety sensitivity is a tendency to misinterpret the sensations that accompany anxiety — irregular breathing, heart palpitations, trembling, flushing, sweating, stomach rumbling — as indications of imminent physical danger or serious illness ("I'm going to have a heart attack;" or "I'm going to faint"), loss of control ("I can't concentrate — I'm going crazy!"), or humiliating social rejection ("Everyone will notice that I'm trembling"). Standard questionnaires have been developed to measure the phenomenon. The most widely used is the Anxiety Sensitivity Index, which asks people to affirm or deny statements like "Unusual body sensations scare me."