Tonya Mosley of FRESH AIR spoke with Michelle Carr, a dream scientist who directs the Dream Engineering Laboratory at the University of Montreal, about why we dream, what causes nightmares, and ways to influence them.
Nightmares are common: most people will have at least one a year, many have them monthly, and roughly 6% of people experience weekly nightmares that interfere with daily life. Whereas nightmares were once thought to be random glitches, Carr argues they are often learned responses that can be changed. Lucid dreaming and a set of techniques sometimes called “dream engineering” let people rehearse, rescript, or otherwise steer dream content.
Why we dream
Contemporary research suggests dreaming helps the brain process recent emotional experiences and memories, forming associations that prepare us for future challenges. In that way, dreaming acts like overnight emotional processing or self-therapy. When memories are intensely emotional — for example after trauma — the normal processing can be interrupted and wake us abruptly, producing nightmares.
Carr’s interest in dream research began with a personal lucid dream during a sleep-paralysis episode in college. Rather than panic, she stayed relaxed and became aware she was dreaming. The vivid, immersive quality of that experience led her to study how the sleeping brain can generate realistic simulations.
How dream labs work
Carr’s lab feels more like a cozy bedroom than a hospital ward. Participants wear electrodes that record brain waves, eye movements, muscle tone, respiration and heart rate. Researchers monitor sleep from an adjacent room, wake people to collect dream reports, and can talk to them through an intercom.
To get better recall, the team asks a focused question on awakening: ‘Can you tell me anything you were experiencing just before I called your name?’ That narrow prompt avoids forcing a full narrative and often brings out sensory fragments, feelings, short thoughts and whole scenes.
Who gets nightmares, and why
People who have many nightmares often share traits: high sensitivity, vivid imagination, strong daydreaming tendencies, empathy and creative minds. For some, intense imagination is a source of artistic inspiration as well as more frequent bad dreams. Nightmares differ from ordinary bad dreams in intensity and effect: when dreams repeatedly interrupt sleep and cause daytime distress, avoidance of sleep, or impaired functioning, they may meet criteria for nightmare disorder and need treatment.
The sleeping body shapes dreams
Dreams are not only mental stories; the body contributes. REM sleep, when most vivid dreaming occurs, features rapid eye movements, heart-rate shifts, twitches and facial expressions. Physical sensations like jaw soreness from teeth grinding can be woven into dream imagery — the familiar teeth-falling-out dream can reflect dental irritation or bruxism. Irregular sleep schedules, deprivation and fragmented sleep increase nightmares by disturbing the normal progression of sleep stages. Stable sleep helps consolidate deep sleep earlier in the night and REM later; disruptions mix stages and raise the chance of upsetting dreams.
Common themes and possible functions
Recurring stress dreams — for example being unprepared for an exam or repeatedly failing at a task — are extremely common and may reflect dreaming’s rehearsal function. In some cases these anxious dreams appear adaptive: studies of medical students found those who had exam-related anxiety dreams sometimes performed better, perhaps because the dreams reinforced rehearsal and motivation.
Early adversity and lasting patterns
Research links childhood adversity, even before age six, to more frequent nightmares in adulthood. Early trauma may alter how emotional processing develops, leaving vivid implicit emotional traces that later surface in dreams even if explicit memories fade. This is an active area of study.
Interventions for children
Many adult treatments can be adapted for kids. Caregivers can help children rewrite recurring nightmares into less threatening versions through storytelling, drawing, or playful ‘‘magic’’ elements. Age-appropriate lucid-dreaming techniques can also give children tools to change outcomes in their dreams, such as choosing to fly away from a threat.
Duration and health effects
Most nightmares happen within a single REM episode; REM periods can last up to 25–30 minutes late in the night, though individual dream experiences are often shorter. Frequent, severe nightmares can cause immediate physical distress — racing heart, sweating, rapid breathing — and lead to daytime fatigue. Chronic nightmares have been linked to higher morning stress hormones, poorer self-reported physical health, possible cardiovascular risk, and some studies suggest associations with earlier mortality, though the causal picture is complex.
Dream enactment and REM behavior disorder
Sometimes intense dream emotions are acted out: crying, shouting, or violent movements. In REM behavior disorder (RBD), the usual muscle paralysis of REM is lost and people physically act their dreams, which can include kicking or punching. RBD is more common in older men and can be an early sign of neurodegenerative conditions such as Parkinson’s disease.
Dream engineering: influencing sleeping minds
Dream engineering covers techniques to influence dream content. Cognitive strategies include visualization and rehearsal before sleep; lab methods use sensory or neural stimulation. Targeted memory reactivation pairs a sensory cue (a sound or light) with a learning task while awake and replays the cue during sleep to reactivate associated memories. In lucid-dream research, brief flashes or tones delivered during REM can be integrated into dream imagery and serve as reminders to become aware.
Home practices to encourage lucidity
Simple, mindfulness-like exercises at bedtime can help: lying still and cycling attention through imagined visual scenes, sounds, and bodily sensations cultivates awareness that can carry into dreams. Regular practice increases the chances of becoming lucid and being able to steer dream content.
Sleep trackers: help and caveats
Wearable sleep trackers can encourage regular schedules and attention to sleep duration, but they’re often inaccurate for people with atypical sleep patterns. Being told you slept poorly by a device can itself worsen perceived restfulness and daytime performance, so treat tracker data as useful guidance rather than definitive diagnosis.
A success story
Carr describes a participant haunted by a realistic tiger dream that began after a break-in. Using visualization and rescripting in the lab, the tiger was transformed into a cartoonish, nonthreatening figure from childhood TV. The change reduced threat, improved the woman’s willingness to sleep, and decreased avoidance behavior — a clear example of how altering a nightmare can improve sleep and daytime wellbeing.
Takeaways
Dreams appear to help process emotions and rehearse challenges. Nightmares, often linked to stress, trauma or disordered sleep, can become habitual but are not necessarily permanent. Techniques from dream engineering — rescripting nightmares, cultivating lucid dreaming, and using carefully timed sensory cues — offer practical ways to reduce distressing dreams. Early, supportive interventions for children, stable sleep schedules, and targeted therapies can transform nightmares and reduce their impact on daily life.