The most distinct consequence of daily stress is increase in rapid-eye-movement (REM) sleep associated with genes involved in cell death and survival.
REM sleep (paradoxical sleep) where we have most of our dreams and regulator of emotions and memory consolidation.
REM sleep disturbances common in mood disorders, such as depression.
During 9-week study mice were exposed to mild stressors, such as the odour of a predator. They developed the following:
- Signs of depression
- less engaged in self-care activities
- less likely to participate in pleasurable activities such as eating appetising food
- less social
- less interested in meeting new mice
Monitoring sleeping patterns saw an increase in the duration and continuity of REM sleep and specific brain oscillations characteristic of REM sleep, whereas ‘deep’ sleep did not change.
The changes in REM sleep were very tightly linked to deficiency in the regulation of the stress hormone corticosterone.
Mild stress also caused changes in gene expression in the brain.
Link between stress and genes
Researchers that REM sleep, the regulation of the stress hormone and a behavioural sign of depression were closely associated with molecular pathways involved in the death and survival of cells in the brain, primarily in the hippocampus.
Increase in REM sleep can activate signalling pathways in the brain which allow it to change in response to ‘mildly stressful’ waking experiences.
The findings provide a better understanding of how changes in sleep contribute to mood disorders.
First author Dr Mathieu Nollet said:
“The comprehensive analysis of the behavioural changes in combination with the sleep and gene expression analyses make a strong case for the important role of REM sleep in the brain response to stress.”
Senior Author Dr Raphaelle Winsky-Sommerer, Reader in Sleep & Circadian Rhythms at the University of Surrey, said:
“The behavioural and sleep changes are very similar to those observed in depression and we therefore believe that the molecular changes observed in mice may also be relevant to the response to stress and mood disorders in humans.”
Professor Derk-Jan Dijk, who leads the Surrey Sleep Research Centre at the University of Surrey, said:
“Once again we see that sleep is a very sensitive and early marker of the brain response to the challenges faced during wakefulness. It now will be important to see how sleep is involved in the recovery from stress.”
The research was supported by a Lilly Innovation Fellowship Award from Eli Lilly and Company Ltd.