context: Thanks to an internal body clock, most people get sleepy and wake up at roughly the same times every day. But if you have Non-24-hour sleep-wake disorder ( Non-24), you may find yourself gradually going to bed later every night and waking up later each day. Eventually, your sleep schedule goes all the way around the clock. For example, you might fall asleep at 11 p.m. one night and then can't get to sleep until 1 a.m. the next night. The delay gets worse until you're going to sleep at 2 a.m., 4 a.m., and later each night. Non-24 is a circadian rhythm disorder and occurs because our internal clock is not synched with light and dark cycles of the day and night. Most individuals with this disorder are totally blind. That's because your internal clock gets its cue from seeing light. But sometimes people who have normal vision also get it. There's no cure, but treatments, including hormones, medicine, and light therapy, can help get you closer to a normal sleeping pattern. Ask your doctor to put you in touch with others who also have Non-24. You can get emotional support from those who are going through the same things you are. You can also get advice in support groups about how to educate your friends, teachers, or bosses about your condition and how it affects your schedule. You might need to bust some myths about it. For example, some people may think all you need to do is "try harder" to get to sleep on time. Explain to them that you've got a very real disorder and that you're getting medical help to try to bring it under control. You get Non-24 because of a problem with your internal body clock, which controls your ability to sleep at night and stay awake during the day. This "clock" is actually a group of thousands of nerve cells in your brain that sends signals to your body that it's time to wake up or go to sleep. Light plays a key role in this process. Your body clock doesn't swing into action until light moves from your eyes to your brain. If you're totally blind, light doesn't reach your brain, so your internal body clock may not work right. About half of all people who are completely blind have Non-24. If you're not blind and you have Non-24, it might be because there are problems in the way your brain is getting light from your eyes. You won't have any vision trouble, but your body clock isn't getting the start-up signal it needs to message your body that it's time to wake up or go to sleep. You could also get Non-24 if your body doesn't make enough melatonin. Other causes include: Developmental brain disorders, including autism spectrum disorder Brain damage from head injury or tumors When you have Non-24 you feel sleepy during the day and have trouble falling asleep at night. Since your sleep schedule moves around the clock, you may feel normal for days and weeks at a time. But as your bedtime pattern shifts, you'll go back to having problems in getting to sleep at night. Non-24 is often mistaken for sleep deprivation or psychiatric problems. Your doctor will ask about your medical history. He may suggest you keep a sleep diary for a few weeks, or even months, to help track your sleep patterns. You may also wear a sensor that tracks your movement and records your rest and activity patterns. Your doctor may ask you questions such as: How often do you fall asleep during the day? Do you feel rested after sleeping? How have your sleep patterns affected your work, personal, and social lives? When was the last time you had a good night's sleep? When you sleep, do you wake up feeling rested? How strong is your desire to sleep during the day, and how does it change from one day to the next? How hard is it for you to concentrate? What do you do to stay awake during the day? Blood, urine, or saliva tests over several weeks can check for signs that your body clock runs on a non-24-hour rhythm. Together, the sleep diary and test results will help your doctor diagnose Non-24-hour sleep-wake disorder. Do I have Non-24 or another circadian rhythm disorder? What tests will I need? How do I keep a sleep diary? What is causing my Non-24? What are the treatments? What do you recommend? What lifestyle changes can help me manage my disorder? Can I ask for accommodations at work or school? The goal is to get your internal body clock back into sync with the rest of the world's 24-hour day-night cycle. You have several options. Phototherapy. You are exposed to bright light early in the morning from a light box. Late in the day, you wear special goggles to avoid light. Doctors usually try light therapy only after your sleep hours are back to normal, and it works only in people who have vision. It helps your eyes send the right signal to your brain about light and dark. Melatonin. This is a hormone that controls the sleep-wake cycle. By taking doses at the right times, you might be able to shift your body clock earlier or later. If you have vision problems, you may need to take other treatments along with it, but it's effective on its own for people who are totally blind. Medication. Your doctor may recommend a prescription drug that targets the parts of the brain that control the timing of the sleep-wake cycle. Treatment is only part of what you can do to manage your condition. Look for creative ways to adjust to your shifting sleep patterns. Think about what's important to you and how you can make positive changes in your life. For instance, you may need to ask your boss for flexible working hours. If you're a student, consider taking classes online or viewing lectures on video. Ask your school about getting a flexible exam schedule or taking a lighter course load. Keep in mind that Non-24 is considered a disability under the Americans with Disabilities Act. Schools and employers must make reasonable accommodations for you, such as part-time or altered schedules. It's important to keep a regular schedule of phototherapy, melatonin, or medication to keep your body clock in tune with a 24-hour day-night cycle. Treatment success varies from person to person. One survey found that a combination of therapies brought "moderate" or "marked" improvement in 31% of people. If you still have some symptoms after treatment, get help from your doctor and family members about managing your lifestyle to fit your changing sleep-wake cycle. You may need advice from a mental health professional to help you work through the challenges of a shifting schedule. Get the emotional backing you need by reaching out to family and friends. You can also get more information about Non-24, along with tips for managing the condition, on the web site of the Circadian Sleep Disorders Network.