Medical Research: What is the background for this study? What are the main findings?
Response: As psychologists we are interested in helping individuals improve their quality of life and reduce their symptoms. We know that many people, including those with anxiety and mood disorders, are bothered by repetitive negative thoughts that feel like they are out of control. We are always looking for new ways that we might be able to reduce these kinds of symptoms. We are specifically interested in learning more about how sleep relates to psychopathology because an extensive literature documents the cognitive and emotional impact of sleep disruption. Therefore, addressing sleep disruption may be another avenue for us to explore for helping out clients. However, there is relatively little research on the relation between sleep timing and psychopathology compared to that studying the relation between sleep duration and psychopathology, despite previous studies showing that individuals who go to bed later than they want to have more disorders characterized by worry, rumination, and obsessing.
This study collected cross-sectional data (i.e., measuring sleep, worry, rumination, and obsessing all at the same point in time) from a group of 100 young adults at Binghamton University. We looked at measures of worry, rumination, and obsessing as well as a newer measure of the process thought to be shared across these psychological phenomena (repetitive negative thinking). We found that people who sleep for shorter amounts of time and go to bed later also have greater levels of worry, rumination, and obsessing. This is called repetitive negative thinking (RNT). We also found that individuals who are classified as “evening type” (i.e., tend to stay up later and shape their daily activities around this schedule), a trait that is linked to biological circadian rhythms, report significantly greater levels of repetitive negative thinking compared to individuals who are “morning” or neither type (i.e., not strongly morning or evening).
This is one of the first studies to show that repetitive negative thinking is related to both how long you sleep and when you sleep.
Medical Research: What should clinicians and patients take away from your report?
Response: Our study showed that repetitive negative thinking was related to variability in sleep duration and sleep timing independent of the shared variability between them. This means they seem to be capturing unique information about an individual’s sleep behavior. We know there are at least two biological systems that control sleep behavior: One that builds the propensity to sleep as a function of how long a person is awake; and another that follows a sine wave pattern across the 24 hour day. Therefore, it may be important for those interested in studying the relation between sleep disruption and psychopathology to consider these different systems in order to best understand how to use this information to help individuals with psychopathology. We are increasingly finding that paying attention to only the amount of sleep a person gets is missing a big part of the picture. For example, individuals with delayed sleep phase disorder, a condition where one gets an adequate number of hours of sleep, but is perpetually misaligned with the light-dark and typical social world schedule have a heightened likelihood of simultaneously having a disorder that is characterized by RNT (e.g., GAD, MDD, OCD). Evidence from other studies suggests that going to bed at a time out of line with one’s circadian rhythms will negatively impact cognitive functions, metabolism, and a whole host of other systems. In particular, cognitive functions are associated with repetitive negative thinking. But, the causal links between these variables have not been evaluated yet. Further studies are needed to determine if modifying bedtimes will actually improve rumination, worry, and obsessing symptoms. Our lab has begun piloting studies to assess these questions.
Medical Research: What recommendations do you have for future research as a result of this study?
Response: At this point, we as scientists are establishing that there is a connection between bedtimes and repetitive negative thinking , but we only have guesses why they are connected. It may be that bedtimes out of alignment with the light-dark cycle may put our bodies and brains into a state of confusion. The careful balance among all of our interacting systems is thrown off. In particular, we hypothesize that the ability to inhibit thoughts and images may be diminished. Further, there is a negative impact on mood. Therefore, individuals who go to bed later may be more prone to experience these repetitive negative thoughts and have trouble dismissing them.
We are continuing our study of the relation between sleep and psychopathology by pursuing more information about the cognitive processes that may connect the two. For example, we are using tasks to assess response inhibition, attention, decision-making, and superstitious beliefs in relation to sleep. We are also using measurements of brain electrical activity to assess error processing in individuals with delayed sleep phase disorder. We are also piloting interventions focused on shifting bedtimes and examining their effects on functioning, including reductions in repetitive negative thinking symptoms.