Daily Stress Causes Disturbances in REM Sleep, Gene Expression Changes

An increase of rapid-eye-movement (REM) sleep is one of the first consequences of daily mild stress, according to a study published in PNAS. The findings also reveal a link between REM sleep and changes in genes involved in cell death and survival.

During REM sleep is when most dreaming occurs, and it is involved in regulation of emotions and memory consolidation. REM sleep disturbances are known to be common in mood disorders, such as depression, but the molecular link to such disorders and REM sleep was not well understood.

In the current study, researchers from the University of Surrey in collaboration with Eli Lilly intermittently exposed mice to mild stressors, such as the smell of a predator. These mice developed signs of depression, including lowered interest in pleasurable activities such as eating appetizing food, and they became less interested in social behaviors.

These changes were accompanied by an increase in the duration and continuity of REM sleep, with no changes in non-REM sleep. These changes in REM sleep were linked to deficiency in regulation of the stress hormone corticosterone. Changes in gene expression in the brain were also observed.

Using a machine-learning approach to identify groups of genes associated with observed sleep, behavioral, and hormonal characteristics, the researchers found that all three changes were associated with apoptotic pathways, particularly in the hippocampus. These findings suggest an important role of REM sleep in response to stress, and the researchers believe these observations likely carry over to humans.