Worry affects the immune response to phobic fear.

Worry, the cognitive enumeration and anticipation of potential future negative events, is associated with autonomic dysregulation, which may in turn have implications for the immune system. People endorsing high (n = 7) and normal levels of trait worry (n = 8) were briefly exposed to a phobic stimulus and the autonomic and immune responses and recovery were assessed. A time-matched control group (n = 6) was not exposed to any stimulus. Both worry groups showed increased heart rate and skin conductance in response to phobic fear. However, only the normal worry group showed a concomitant increase in natural killer cells in peripheral blood. Patterns of change during the follow-up period suggested that phobic fear had disrupted a normal circadian increase in natural killer cells. Adrenergic and hypothalamus-pituitary-adrenal mechanisms may be responsible for the differences between high and normal worry groups in their natural killer cell response to and recovery from phobic fear.