Reactivity to imagery and nocturnal panic attacks.

We assessed psychophysiological responses to imagery of traumatic events, panic attacks, and loss of vigilance (i.e., being hypnotized) in participants diagnosed with panic disorder. Participants were either currently experiencing nocturnal panic or daytime panics only. It was hypothesized that nocturnal panickers would exhibit heightened responsivity to imagery of their worst panic and worst trauma, as well as being hypnotized, compared to day panickers. Using established imagery procedures, heart rate, skin conductance, and frontalis electromyogram were recorded as participants imagined each scene. Nocturnal and day panickers differed in their responses to the hypnosis scene only. As predicted, nocturnal panickers endorsed more panic symptoms in response to imagery of being hypnotized. Contrary to expectation, nocturnal and daytime panickers showed no differences in physiologic reactivity or self-reported distress to worst trauma or worst panic imagery. The findings are discussed with respect to the role of fear of loss of vigilance for nocturnal panic.