As you might imagine, nightmares not only spiked the CAR of participants, but they also caused a reported decrease in mood and overall health, compared to neutral dreams. Things like rumination, health complaints, and reduced sleep quality were also reported. And these effects carried into the day upon waking up.
Based on the findings, the team suggests that factors affecting sleep, namely nightmares, contribute to varying levels in the CAR every morning—big news for anyone who often wakes up in the mornings feeling anxious.
“This has important methodological implications for CAR studies in general,” the study authors note, “and might have even more relevance for studies in clinical populations suffering from chronic sleep disturbances.”