Hypersomnia, or excessive sleepiness, is a condition in which a person has trouble staying awake during the day. People who have hypersomnia can fall asleep at any time; for instance, at work or while they are driving. They may also have other sleep-related problems, including a lack of energy and trouble thinking clearly.

According to the National Sleep Foundation, up to 40% of people have some symptoms of hypersomnia from time to time.

Hypersomnia causes excessively sleepy during the day even after a good or prolonged night's sleep. It also makes it difficul to wake up after you've been asleep at night or for a nap. Naps generally aren't refreshing.

The need to sleep can strike at any time, including when you're driving a car or working, which makes idiopathic hypersomnia potentially dangerous.

The condition often develops over weeks to months. 

There are several potential causes of hypersomnia, including:

• The sleep disorders narcolepsy (daytime sleepiness) and sleep apnea (interruptions of breathing during sleep)
• Not getting enough sleep at night (sleep deprivation)
• Being overweight
• Drug or alcohol abuse
• A head injury or a neurological disease, such as multiple sclerosis or Parkinson's disease
• Prescription drugs, such as tranquilizers or antihistamines
• Genetics (having a relative with hypersomnia)
• Depression

Because the cause of idiopathic hypersomnia isn't known, the treatment is aimed at easing symptoms. Stimulant medication, such as modafinil (Provigil), might be prescribed to help you stay awake during the day.

In addition, your doctor might recommend that you develop a regular nighttime sleep schedule and avoid alcohol and medications that can affect your sleep.

Research shows that people whose ADHD symptoms are severe are more likely to have ADHD that persists into the teen years. ADHD also tends to continue into the teen years for people who also have conduct and depression disorders.

Some common risk factors for ADHD include:

• having a parent who smoked cigarettes or used alcohol during pregnancy
• having a parent who was exposed to lead or other environmental toxins while pregnant
• having a low birth weight
• experiencing a brain injury