Insomnia is the experience of having trouble falling asleep or staying asleep during the night. It may cause you problems during the day, such as tiredness, low energy, poor concentration, and irritability.
Most people experience insomnia at some point in their lives, but the risk of insomnia increases with age and with serious illnesses, such as cancer.
Insomnia often causes other cancer-related conditions and symptoms —such as pain, fatigue, or depression or anxiety—to worsen. It may also decrease your ability to cope with cancer and cause feelings of isolation.
To understand the cause of the insomnia, which helps determine how to treat it, your doctor may ask about the following factors that can contribute to difficulty sleeping:
- A history of a sleep disorder
- Emotional distress or worry
- Depression or anxiety 
- Delirium  (confusion)
- Pain, shortness of breath , a cough, nausea , or itching
- Use of caffeine, alcohol, or tobacco
- Any new medications or side effects of other medications
- Withdrawal from medication
- Hormonal changes (for example, when a woman experiences menopause or a man experiences andropause [a drop in testosterone]) or symptoms of hormonal changes, such as hot flashes, which tend to be worse at night
- Poor sleep habits
- An unfamiliar, noisy, or uncomfortable sleep environment
- History of snoring or stopping breathing
- Daytime sleepiness
- Falling asleep doing routine activities (for example, driving a car, when stopped at a red light, when reading)
- Recent weight gain
- Exercising right before bedtime
- Restless legs
Relieving side effects—also called symptom management, palliative care , or supportive care—is an important part of cancer care and treatment. Talk with your health care team about any symptoms you experience, including any new symptoms or a change in symptoms.
The goal for managing insomnia is to achieve restful sleep and improve your overall quality of life.
First, identify potential sources of the insomnia—such as pain, depression, anxiety, stimulating medications, or sleep disorders—and ask your doctor or nurse to help you manage these conditions. If insomnia is an ongoing problem, your doctor may have you undergo an overnight sleep study to help determine whether you have other types of sleep disorders, such as sleep apnea (a temporary pause or decrease in the flow of air while breathing during sleep), that may be affecting your ability to fall asleep or stay asleep.
Medications may help relieve insomnia but should only be used in the short term, unless other treatments are ineffective. Behavioral techniques are usually more effective for long-term relief. Learn more about strategies for a better night's sleep , including engaging in healthy daytime habits, exercising, developing a bedtime routine, making changes to your sleeping area, reducing stress, and keeping a diary of your sleep-related behaviors.