REM Rebound Effect

Neurophysiological and hormonal processes are vital for maintaining normal sleep patterns and homeostasis. A healthy sleep structure is essential for promoting and safeguarding physical and mental well-being. Sleep provides numerous benefits, including energy conservation, physical recuperation, brain plasticity enhancement, memory consolidation, emotion processing, and cognitive integration. Disrupted sleep activates the body's natural mechanisms to restore a balanced sleep cycle. Sleep involves distinct phases characterized by temporary disconnection from the external environment, reduced consciousness, muscle atonia, and changes in metabolism. Please see StatPearls' companion resource, "Physiology, REM Sleep," for more information. Sleep is categorized into 2 stages—rapid eye movement (REM) and non-REM (NREM) sleep. Under normal conditions, individuals progress through a predictable sequence of stages, starting with wakefulness, moving through various NREM stages, and eventually entering REM sleep. In adults, REM sleep accounts for 20% to 25% of total sleep time, occurring every 90 to 120 minutes and increasing in duration with each cycle. Typically, there are 4 to 5 periods of REM sleep per night. REM sleep is characterized by ocular saccadic movements, muscle atonia, and fast-wave electroencephalography (EEG) patterns that resemble the waking state and are associated with dream-like activity. NREM sleep consists of 3 stages—N1, N2, and N3—each exhibiting distinct EEG wave patterns. The REM rebound effect is a compensatory response in which an individual experiences increased REM sleep temporarily. REM sleep is characterized by vivid dreams accompanied by REMs, paralysis of skeletal muscles, and EEG patterns indicating an activated cerebral cortex. When mammals and birds experience sleep deprivation, it increases the pressure to sleep and achieve REM rebound once they do sleep. For instance, horses can stand while in non-REM sleep but must lie down to enter REM sleep safely. If they are unwilling or unable to lie down, the pressure to enter REM sleep may cause them to do so while standing, leading to a sudden loss of muscle tone and a risk of dangerous falls.  Several factors can cause REM rebound and an increase in REM sleep percentage, including REM sleep deprivation, withdrawal from REM-suppressing medications (such as selective serotonin reuptake inhibitors), substance withdrawal (eg, alcohol or cocaine), depression, and CPAP titration. Experimental studies utilizing EEG and hormonal assays demonstrate that human and animal subjects experiencing sleep deprivation or significant stressors exhibit an amplified frequency and intensity of REM sleep as a compensatory mechanism. REM sleep is important in brain maturation, maintaining minimal brain activity during sleep, memory consolidation, supporting brain neurotransmitter systems, and regulating emotions. REM rebound following stress serves as an important adaptive function (see Hypnogram of Sleep Stages and Cycles).