Why do you have nightmares in your sleep?

Nightmares can be caused by stress, mental health problems, drug use or nocturnal eating habits.

Nightmares are a common phenomenon during sleep. About 85% of adults have had at least one nightmare within the past year. According to a survey published in the journal PubMed, about 4-10% of people report having nightmares one or more times a week. This phenomenon is more common in women, children and people diagnosed with mental illnesses.

Experts don’t have a universal answer for why people have nightmares. They think this phenomenon occurs when the body tries to reassemble memories, regulate mood and process experiences when people are awake. Some researchers theorize that nightmares are a manifestation of a normal process, while others suggest that it is an unusual phenomenon.

Although they have not come to a final conclusion, scientists still come up with some basic factors that cause nightmares.


Nightmares occur more often during periods of stress, when a person experiences major life changes. Research shows that the content of dreams often reflects the source of stress while awake.

Illustration of a person having a nightmare while sleeping. Image: Freepik

While this can cause anxiety, some researchers suggest that nightmares can help reduce stress. Many nightmares represent the body’s attempt to respond positively to daytime stressors, researchers say.

Mental health problems

Nightmares can be linked to many mental health problems, including depression, anxiety disorders, bipolar disorder, schizophrenia, and post-traumatic stress disorder (PTSD).

Nightmares are a hallmark symptom of PTSD, affecting 72% of people with the syndrome. For many patients, nightmares are a self-soothing mechanism for traumatic experiences, helplessness, and lack of control.

Using drugs

Certain medications can increase a user’s risk of nightmares, such as antidepressants, tranquilizers, and narcotics. Stopping medication after a while can also lead to nightmares.

Many medications such as barbiturates and benzodiazepines reduce the amount of REM (dream phase) sleep each night. When a patient stops taking the drug, the body experiences a condition called “REM recovery”. During REM recovery, the body tries to catch up with the lost sleep. Since the majority of nightmares occur during REM sleep, some people are at risk for nightmares and vivid dreams.

Melatonin is a sleep-promoting hormone that is naturally produced by the body. Many people also take melatonin as an over-the-counter sleeping pill and report nightmares after using it. However, there is currently very little research regarding this potential side effect. One potential explanation is that melatonin supplementation is increasing the duration of REM sleep, which in turn increases the chances of nightmares or other types of vivid dreams.

Sleep disorders

Certain sleep disorders such as insomnia, sleep apnea, and narcolepsy can increase the risk of nightmares. Nightmares are reported in about 17% of people with chronic insomnia and 33% of people diagnosed with narcolepsy.

A person is diagnosed with nightmare disorder if the condition recurs repeatedly and interferes with daily activities. Nightmare disorder is a type of sleep disorder, also known as parasitic insomnia.

Nocturnal panic attacks are another form of parasitic insomnia, characterized by panic attacks during sleep, restless sleep, kicking, flailing limbs, and even screaming.

Eat before sleeping

Eating too close to bedtime can increase the risk of nightmares. In a study published in the journal PubMed, 9.5% of people surveyed reported that eating late at night influenced the content of their dreams. They don’t know if the meal led to the nightmare or if there was another reason for the phenomenon.

Thuc Linh (Follow Sleep Doctor)


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