Insomnia is a persistent disorder that can make it hard to fall asleep, hard to stay asleep or both, despite the opportunity for adequate sleep. With insomnia, you usually awaken feeling unrefreshed, which takes a toll on your ability to function during the day. Insomnia can sap not only your energy level and mood but also your health, work performance and quality of life.

How much sleep is enough varies from person to person. Most adults need seven to eight hours a night.

Many adults experience insomnia at some point, but some people have long-term (chronic) insomnia. Insomnia may be the primary problem, or it may be secondary due to other causes, such as a disease or medication.

You don't have to put up with sleepless nights. Simple changes in your daily habits can often help.

Insomnia symptoms may include:

• Difficulty falling asleep at night
• Awakening during the night
• Awakening too early
• Not feeling well rested after a night's sleep
• Daytime tiredness or sleepiness
• Irritability, depression or anxiety
• Difficulty paying attention, focusing on tasks or remembering
• Increased errors or accidents
• Tension headaches
• Distress in the stomach and intestines (gastrointestinal tract)
• Ongoing worries about sleep

Someone with insomnia will often take 30 minutes or more to fall asleep and may get only six or fewer hours of sleep for three or more nights a week over a month or more.

Common causes of insomnia include:

Stress. Concerns about work, school, health or family can keep your mind active at night, making it difficult to sleep. Stressful life events — such as the death or illness of a loved one, divorce, or a job loss - may lead to insomnia.

Anxiety. Everyday anxieties as well as more-serious anxiety disorders, such as post-traumatic stress disorder, may disrupt your asleep. Worry about being able to go to sleep can make it harder to fall asleep.

Depression. You might either sleep too much or have trouble sleeping if you're depressed. Insomnia often occurs with other mental health disorders as well.

Medical conditions. If you have chronic pain, breathing difficulties or a need to urinate frequently, you might develop insomnia. Examples of conditions linked with insomnia include arthritis, cancer, heart failure, lung disease, gastroesophageal reflux disease (GERD), overactive thyroid, stroke, Parkinson's disease and Alzheimer's disease.

Change in your environment or work schedule. Travel or working a late or early shift can disrupt your body's circadian rhythms, making it difficult to sleep. Your circadian rhythms act as an internal clock, guiding such things as your sleep-wake cycle, metabolism and body temperature.

Poor sleep habits. Poor sleep habits include an irregular sleep schedule, stimulating activities before bed, an uncomfortable sleep environment, and use of your bed for activities other than sleep or sex.

Medications. Many prescription drugs can interfere with sleep, including some antidepressants, heart and blood pressure medications, allergy medications, stimulants (such as Ritalin), and corticosteroids. Many over-the-counter (OTC) medications  including some pain medication combinations, decongestants and weight-loss products  contain caffeine and other stimulants.

Caffeine, nicotine and alcohol. Coffee, tea, cola and other caffeine-containing drinks are well-known stimulants. Drinking coffee in the late afternoon and later can keep you from falling asleep at night. Nicotine in tobacco products is another stimulant that can cause insomnia. Alcohol is a sedative that may help you fall asleep, but it prevents deeper stages of sleep and often causes you to awaken in the middle of the night.

Eating too much late in the evening. Having a light snack before bedtime is OK, but eating too much may cause you to feel physically uncomfortable while lying down, making it difficult to get to sleep. Many people also experience heartburn, a backflow of acid and food from the stomach into the esophagus after eating, which may keep you awake.

Insomnia and aging

Insomnia becomes more common with age. As you get older, you may experience:

A change in sleep patterns. Sleep often becomes less restful as you age, and you may find that noise or other changes in your environment are more likely to wake you. With age, your internal clock often advances, which means you get tired earlier in the evening and wake up earlier in the morning. But older people generally still need the same amount of sleep as younger people do.

A change in activity. You may be less physically or socially active. A lack of activity can interfere with a good night's sleep. Also, the less active you are, the more likely you may be to take a daily nap, which can interfere with sleep at night.

A change in health. The chronic pain of conditions such as arthritis or back problems as well as depression, anxiety and stress can interfere with sleep. Older men often develop noncancerous enlargement of the prostate gland (benign prostatic hyperplasia), which can cause the need to urinate frequently, interrupting sleep. In women, menopausal hot flashes can be equally disruptive.

Other sleep-related disorders, such as sleep apnea and restless legs syndrome, also become more common with age. Sleep apnea causes you to stop breathing periodically throughout the night. Restless legs syndrome causes unpleasant sensations in your legs and an almost irresistible desire to move them, which may prevent you from falling asleep.

More medications. Older people typically use more prescription drugs than younger people do, which increases the chance of insomnia caused by a medication.

Sleep problems may be a concern for children and teenagers as well. However, some children and teens simply have trouble getting to sleep or resist a regular bedtime because their internal clocks are more delayed. They want to go to bed later and sleep later in the morning.

Nearly everyone has an occasional sleepless night. But your risk of insomnia is greater if:

You are a woman. Women are much more likely to experience insomnia. Hormonal shifts during the menstrual cycle and in menopause may play a role. During menopause, night sweats and hot flashes often disturb sleep. Insomnia is also common with pregnancy.

You are older than age 60. Because of changes in sleep patterns and health, insomnia increases with age.

You have a mental health disorder. Many disorders — including depression, anxiety, bipolar disorder and post-traumatic stress disorder — disrupt sleep. Early-morning awakening is a classic symptom of depression.

You are under a lot of stress. Stressful events can cause temporary insomnia. And major or long-lasting stress, such as the death of a loved one or a divorce, can lead to chronic insomnia. Being poor or unemployed also increases the risk.

You work night or changing shifts. Working at night or frequently changing shifts increases your risk of insomnia.

You travel long distances. Jet lag from traveling across multiple time zones can cause insomnia.

Complications

Sleep is as important to your health as a healthy diet and regular exercise. Whatever your reason for sleep loss, insomnia can affect you both mentally and physically. People with insomnia report a lower quality of life compared with people who are sleeping well.

Complications of insomnia may include:

• Lower performance on the job or at school
• Slowed reaction time while driving and higher risk of accidents
• Psychiatric problems, such as depression or an anxiety disorder
• Overweight or obesity
• Irritability
• Increased risk and severity of long-term diseases or conditions, such as high blood pressure, heart disease and diabetes.
• Substance abuse.