Stability of nightmare frequency and its relation to neuroticism: A longitudinal study.

Models of nightmare aetiology postulate an interaction between trait and state factors. However, most of the studies that support these models have been cross-sectional and longitudinal studies are scarce. The present data were obtained from N = 888 participants completing two online dream studies carried out independently with the same online panel 2 years apart. Nightmare frequency declined over the 2-year period and these changes were related to changes in neuroticism. The effect of current psychopathology (state aspect) on nightmare frequency was significant but much smaller compared to the effect of previously measured nightmare frequency (trait aspect) and, thus, the study provided empirical evidence for diathesis-stress models. Future longitudinal studies should take a closer look at life events and other factors that increase and/or decrease nightmare frequencies.