Sleeping Problems: Hypersomnia or Somnolence Syndrome or Nightmares

Approved by the Cancer.Net Editorial Board, 10/2017

Cancer and its treatment may cause the following sleeping problems:

  • Hypersomnia

  • Somnolence syndrome

  • Nightmares

  • Insomnia

Other factors may also cause these sleeping problems. These include emotional concerns and medical conditions unrelated to cancer.

Relieving side effects is an important part of cancer care and treatment. Treatment to manage side effects is called palliative care or supportive care. Talk with your health care team about managing or coping with sleeping problems.


People with hypersomnia feel very sleepy during the day. Or they want to sleep for longer than normal at night. Hypersomnia is also called somnolence, excessive daytime sleepiness, or prolonged drowsiness.

Signs of hypersomnia

The signs of hypersomnia can include:

  • Sleeping for 10 or more hours at a time

  • Excessive amounts of deep sleep

  • Trouble staying awake during the day

  • Excessive sleepiness that is not reduced by taking a nap 

Hypersomnia may interfere with your relationships and prevent you from enjoying activities. It can also make handling daily activities and family and work responsibilities a challenge.

Although similar, hypersomnia and fatigue are not the same. Fatigue is a feeling of exhaustion and lack of energy not relieved by sleep. Excessive daytime sleeping and being unable to stay awake are not signs of fatigue.

Causes of hypersomnia

The following types of cancer, cancer treatment, and other medical conditions can cause hypersomnia:

  • Brain and central nervous system tumors

  • Pancreatic cancer

  • Any cancer that has spread from 1 part of the body to another, including to the brain

  • Some types of chemotherapy

  • Prescription and over-the-counter medications, such as:

    • Some antidepressants

    • Antinausea medications

    • Some pain medications

    • Sedatives, which calm or cause sleep

    • Antihistamines, which treat allergy and cold symptoms

    • Sleeping pills

  • Anemia or a low red blood cell count

  • Changes in hormone levels in the body

  • Sleep apnea, which is a short pause or decrease in air flow while breathing during sleep. This can cause snoring.

  • Other symptoms of cancer or side effects of cancer treatments, such as the following:

    • Hypercalcemia, which is a high level of calcium in the blood

    • Hypokalemia or low levels of potassium

    • Hypothyroidism, which is when the thyroid gland does not make enough thyroid hormones

    • Depression

Managing hypersomnia

To treat hypersomnia, your doctor first needs to find and treat the cause. This is the most effective way to relieve the symptoms. For example, hypersomnia related to chemotherapy usually improves after treatment ends. If other medications are causing it, your doctor may be able to switch to a different medication or adjust the dose. Your doctor may also prescribe stimulant medications to help you stay awake during the day.

The following behavioral changes may help you manage hypersomnia:

  • Sleep a few hours longer at night to avoid excessive sleepiness during the day.

  • Exercise daily in the morning or early afternoon, if possible. Avoid heavy exercise 3 to 4 hours before bedtime.

  • Do enjoyable activities that require your full attention.

  • Try to go to sleep and wake up at the same time every day.

  • Get out of bed and stay out of bed until bedtime.

  • Avoid heavy meals and foods that make you sleepy during the day.

  • Avoid alcohol and caffeine for several hours before bedtime.

  • Avoid using screens such as computers or TV for several hours before bedtime. Try reading an enjoyable book instead.

  • Make your bedroom quiet and cool.

Somnolence syndrome

Somnolence syndrome is a type of hypersomnia in children. It is associated with radiation therapy to the head.

Symptoms of somnolence syndrome

The symptoms of somnolence syndrome usually occur 3 to 12 weeks after radiation treatment ends. They can last a few days or several weeks. The symptoms include:


Nightmares are vivid, frightening dreams. They usually cause the person to wake up and remember part or most of the dream.

Most people have nightmares from time to time. But the frequency or vividness of nightmares can increase after a cancer diagnosis and during cancer treatment. Frequent nightmares can lead to a fear of going to sleep, restless sleep, and daytime sleepiness.

Causes of nightmares

An increase in emotional stress commonly causes nightmares. It may be a way in which the mind works through unresolved feelings and fears.

Other causes of nightmares may include:

  • Antibiotics

  • Iron supplements

  • Pain medications

  • Heart medications

  • Withdrawal from alcohol, pain medications, and some anti-anxiety medications

  • Unrelieved pain  

Coping with nightmares

Having cancer is frightening and stressful. So it is normal to experience some nightmares during treatment and recovery. The following tips may help you cope with nightmares:

  • Be honest about your fears and feelings. Discuss them with a family member or friend early in the day, rather than at night.

  • Talk about the nightmares with a family member or friend.

  • Find creative ways to express the content or themes of the nightmares, such as writing about them or drawing pictures.

  • Make up different endings or storylines to the nightmares, and visualize them.

Remember that nightmares are not real. They also do not predict the future or cause bad things to happen. Talk with your health care team or a trained counselor if your nightmares increase or continue, cause excessive anxiety, or prevent you from sleeping well.

Related Resources

8 Steps to a Restful Night’s Sleep

Side Effects