Non-24 can cause insomnia at night coupled with lower alertness during the day, making it extremely difficult for people to thrive in the workplace or engage in social activities.
Tips and facts

Eight facts about non-24

An estimated 70 percent of people who are blind suffer from this little-known condition that causes sleepless nights and chronic fatigue.

A good night’s sleep can be hard to come by if you are blind and have a common disorder known as Non-24. At a recent information session held at Perkins School for the Blind, Vanda Pharmaceuticals’ medical science liaison Aaron Sheppard explained the science behind Non-24, which affects a majority of the world’s blind population. Here are eight things you might not know about this condition:

  1. Non-24 is short for Non-24 Hour Sleep-Wake Disorder, but the condition goes by many other names, including Free Running Disorder, Hypernychthemeral Disorder and Circadian Rhythm Disorder.
  2. Non-24 is caused by the body’s inability to align its day/night circadian rhythms with the surrounding environment. For people who are sighted, light acts as the body’s cue to align its internal clock with a 24-hour day. For people who are blind and lack light perception, the body acts according to its natural circadian rhythm, which may be longer or shorter than 24 hours.
  3. Individuals who are sighted can also suffer from Non-24, although it is rare. In some cases, the cause is unknown. In other cases, sighted people can develop Non-24 after suffering brain injuries or head trauma.
  4. Symptoms of Non-24 include insomnia at night coupled with lower alertness during the day. The sleep deprivation can make it extremely difficult for people who suffer from Non-24 to thrive in the workplace or engage in social activities, and can lead to cognitive dysfunction and depression. 
  5. The first case of Non-24 was recorded in 1970 by three scientists from the University of Manchester (U.K.), who studied a sighted man unable to live according to a 24-hour day. They later published their findings in a paper entitled “A man with too long a day.”
  6. It is estimated that up to 70 percent of people who are totally blind suffer from Non-24. The disorder can affect anyone at any age, from children to adults.
  7. Vanda Pharmaceuticals received FDA approval in 2014 to produce the first-ever treatment for Non-24 for people 18 and older. The drug, known as Hetlioz, acts on receptors in the brain for melatonin, a hormone that helps to control the sleep-wake cycle.
  8. Despite its prevalence among the blind population, many individuals don’t know they have Non-24. This can be attributed to the cyclical nature of the disorder, which can cause severe insomnia for a week, followed by three weeks of restful nights. Doctors also commonly mistake Non-24 for depression or other sleep disorders.

For more information about Non-24, visit the Non-24-Hour Disorder Resource or the National Sleep Foundation.

Eight facts about Non-24 infographic


The Impact of Vision Loss in Development and the Importance of Collaboration to Support the Child

A series of polariods depicting the Perkins Class of 1972, Marie as a student, Marie as an adult on the phone, and Marie with her guide dog.

Perkins alumna Marie Hennessy chooses to give back to her community


Access tech, advocacy, and living with blindness: A conversation with Jonathan Mosen