Dreaming as Overnight Therapy: How REM Sleep Heals Emotional Wounds

We often hear the phrase, “time heals all wounds.” But what if the truth is more nuanced? Research in sleep science suggests that it may not be the mere passage of time that heals, but the time we spend dreaming.

Dr. Matthew Walker, a neuroscientist and sleep researcher, has proposed and tested what he calls the theory of “overnight therapy.” According to this theory, REM sleep—the stage of sleep when most vivid dreaming occurs—acts as a natural emotional balm, helping us process painful memories and strip away their sharp emotional sting.

During REM sleep, the brain undergoes remarkable changes. Levels of noradrenaline, a stress-related chemical, are shut off entirely—the only time in a 24-hour cycle when the brain is free of this anxiety-triggering molecule. Meanwhile, emotion- and memory-related brain structures such as the amygdala, hippocampus, and emotion-related regions of the cortex reactivate.

This unique neurochemical environment allows the brain to replay and reprocess emotional memories in a safe space—reactivating them, but without the surge of stress hormones that would otherwise keep the trauma raw. The result is that we wake up remembering the event, but with less of the painful emotional charge attached.

In Walker’s studies, participants who slept between exposure to emotional images showed both a reduction in how distressed they felt and a measurable dampening of activity in the amygdala, the brain’s emotional alarm center. Those who stayed awake showed no such relief—if anything, their emotional reactivity grew stronger over time.

Dream content also matters. Dr. Rosalind Cartwright’s research demonstrated that patients who dreamed specifically about their recent emotional traumas were more likely to recover from depression related to those events, compared to those who did not dream about the painful themes. This highlights that REM sleep is not only necessary, but that dreaming about our struggles may be the key to emotional healing.

These findings help explain why PTSD patients, who often suffer disrupted REM sleep and repetitive nightmares, struggle to move past their trauma. Their brains may be unable to strip away the emotion from painful memories, leaving them stuck in a cycle of reliving trauma night after night. Treatments such as prazosin, which reduces stress-related brain chemicals during REM sleep, are now being explored to restore this natural healing mechanism.

Sleep, and in particular REM sleep, is far more than rest—it is an emotional reset button. By giving the brain a chance to safely reprocess painful experiences, dreams perform an elegant form of overnight therapy, helping us heal and move forward.

Reference:

Walker, M. (2017). Why We Sleep: Unlocking the Power of Sleep and Dreams. Scribner.