Tonya Mosley of FRESH AIR interviews Michelle Carr, a dream scientist and director of the Dream Engineering Laboratory at the University of Montreal, about why we dream, why nightmares happen and how we can influence them.
Nightmares are common—most people will have at least one a year, many monthly, and up to about 6% of people experience weekly nightmares that disrupt life. For decades many considered nightmares random misfires. Carr argues they are learned responses that can be unlearned through lucid dreaming and “dream engineering”—methods that help people rewrite or influence dream content.
Why we dream
Dream science suggests dreams help process recent emotional experiences and memories, making associations that prepare us for future challenges. Dreaming acts like an overnight form of emotional processing or “self-therapy.” When memories are intensely emotional—especially after trauma—the normal processing can be disrupted and jolt us awake as nightmares.
Carr’s path into the field began with a lucid dream during a sleep-paralysis episode in college. Instead of panicking, she relaxed and stayed asleep, becoming aware she was dreaming. The vivid, immersive experience sparked her interest in how the sleeping brain generates realistic simulations.
Studying dreams in the lab
Carr’s lab resembles a comfortable bedroom rather than a clinical ward. Subjects are fitted with electrodes to record brain activity, eye movements, muscle tone, respiration and heart rate. Researchers monitor sleep from an adjacent room, wake participants to collect dream reports and can interact by intercom.
To improve recall, Carr’s team asks a simple, specific question on awakening: “Can you tell me anything you were experiencing just before I called your name?” This avoids biasing participants toward narrative-only dreams and yields richer reports of thoughts, feelings, sensory fragments and full dream scenes.
Nightmare-prone people: sensitivity and creativity
Carr found that people prone to nightmares tend to be highly sensitive—perceptive, empathetic, creatively vivid. They often report immersive daydreaming and strong imaginations. For some, nightmares coexist with lucid dreaming and artistic inspiration.
Bad dreams vs nightmare disorder
Bad dreams are common and less intense. Nightmares typically interrupt sleep and, when severe and frequent enough to cause daytime distress, avoidance of sleep, or impaired functioning, they qualify as a nightmare disorder requiring treatment.
How the body shapes dreams
Dreams are not purely mental: the sleeping body contributes. REM sleep—the stage most associated with vivid dreams—features heart rate changes, muscle twitches, rapid eye movements and facial expressions. Physical sensations (like jaw soreness from teeth grinding) can be woven into dream imagery; the classic teeth-falling-out dream may reflect dental irritation or bruxism.
Sleep timing and REM
Irregular schedules, sleep deprivation and fragmented sleep increase nightmares. Consistent sleep supports consolidated cycles—deep sleep early and REM later—whereas disruption mixes stages and raises the chance of bad dreams. Nightmares occur most often in REM, a brain state that looks wake-like and carries strong emotional activation.
Common nightmare themes and possible functions
Recurring “work” or stress dreams—e.g., being unprepared for an exam, repeatedly failing at a task—are widespread (up to 75% experience such dreams). These may reflect dreaming’s role in rehearsal and practice, helping to mentally simulate challenges. Sometimes even anxious dreams can be adaptive; one study found medical students who had anxiety exam-dreams performed better on tests, perhaps due to rehearsal or motivation.
Childhood adversity and lifelong patterns
Research links early childhood adversity (even before age 6) to more frequent nightmares in adulthood. Early trauma may alter emotional processing development and lead to vivid encoding of adverse experiences; even if explicit memories fade, implicit emotional traces may persist and manifest in dreams. This remains an area of active investigation.
Interventions for children
Treatments that work for adults apply to children. Caregivers can help children rewrite recurring nightmares into empowering or playful versions—using imagination, drawing or introducing benign “magic” elements. Teaching children lucid-dreaming techniques (age-appropriate) can let them choose safer dream outcomes, like flying away from threats.
Duration and health effects
Most nightmares likely occur within a single REM period; REM episodes range up to 25–30 minutes, though individual dreams are often much shorter. Frequent, severe nightmares can produce immediate physical distress—pounding heart, sweating, rapid breathing—and daytime fatigue. Studies link chronic nightmares to elevated morning stress hormones, self-reported poorer physical health, possible cardiovascular risk and some research even suggests associations with earlier mortality.
Dream enacting and REM behavior disorder
Sometimes dream emotions translate into bodily actions: crying, shouting or more violent acting out. REM behavior disorder (RBD) involves people physically acting dreams—kicking, punching—often in men over 60, and can be an early indicator of neurodegenerative diseases like Parkinson’s. In RBD, the usual muscle paralysis of REM sleep is lost, permitting enactment of dream content and often signaling underlying neurological change.
Dream engineering: influencing sleeping minds
Dream engineering encompasses techniques to influence dream content. Methods range from cognitive strategies (visualization, rehearsal before sleep) to direct sensory or brain stimulation in labs. One lab technique, targeted memory reactivation, pairs sensory cues (lights, tones) with a learning task before sleep, then replays cues during sleep to reactivate associated memories. In lucid-dreaming research, cues presented during REM (a flash of light or sound) can appear within dreams and serve as reminders to become aware and lucid.
Home practices for lucid dreaming
At home, mindfulness-like exercises help: lying still before sleep and cycling attention through senses—visual impressions with eyes closed, sounds, bodily sensations—cultivates the kind of awareness useful for recognizing dream states later. Regular practice increases the chance of becoming lucid in dreams.
Sleep trackers: benefits and cautions
Wearable sleep trackers can encourage consistent schedules and awareness of sleep duration, but they can be inaccurate, especially for atypical sleepers. False negative reports of “poor” sleep can worsen subjective restfulness and performance, since simply being told you slept poorly can impair cognition.
Success story
Carr describes a participant with a lifelong recurring nightmare of a realistic tiger chasing her—triggered by an early break-in. Through visualization and rescripting in the lab, the tiger transformed into a cartoon reminiscent of a childhood show, reducing threat and changing her relationship to sleep. She began going to bed earlier and no longer avoided sleep, illustrating how altering a nightmare can improve sleep habits and daytime wellbeing.
Takeaways
Dreams appear to serve emotional-processing and rehearsal functions. Nightmares, often tied to stress, trauma or disrupted sleep, can become habitual but are not necessarily permanent. Techniques from dream engineering—rescripting nightmares, cultivating lucid dreaming, using sensory cues—offer ways to gain control and reduce the disruptive cycle of chronic nightmares. Early interventions for children, attention to sleep schedule and targeted therapies can help transform distressing dreams and their impact on daily life.
