Quick, list all the sleep disorders you can think of!

If you came up with a list that includes the likes of insomnia, sleep apnea, and/or restless leg syndrome, congrats—you have a basic awareness of some of the most common sleep disorders. But I’m willing to bet Free Running Disorder (FRD) probably didn’t show up on the list.

That’s because this sleep disorder is both rare and complicated, which means it receives very little press coverage and researchers are still figuring out exactly what it entails. But it’s still valuable to be in the know, because it will serve you in the event that you or someone you know develops relevant symptoms. Here’s what we know so far about FRD.

What Free Running Disorder Is All About—And Why It Matters

Just what is FRD, exactly? As far as experts can tell, Free Running Disorder is a rare sleep disorder that stems from an issue with a person’s circadian rhythms.

Our circadian rhythms function like a “body clock” that signals our bodies when it’s time to go to sleep and wake up every day. Normally, these rhythms inspire a fairly consistent sleep-wake routine.

But for people with FRD, these rhythms are much more variable. Instead of signaling someone to go to sleep around the same time every night, they continually shift later and later. So someone might feel sleepy at 11 p.m. one night, but not sense that it’s time to go to bed until 1 a.m. the next night and then 3 a.m. the next night, and so on—so that sometimes, a person’s body tries to force them to sleep in the middle of the day.

Why does this matter? Because it can make it difficult to fall or stay asleep at the same time every night, which is important for maintaining a healthy sleep schedule and being able to function at work, at home, and so on.

In fact, living with FRD can be so stressful that some people with the condition also struggle with depression, anxiety, and tense relationships with people who don’t understand the impacts of the condition. Other consequences of FRD relate to the sleep deprivation it may cause, which can result in fatigue, diminished work performance, an impaired immune system, and reduced capacities for concentration, creativity, and problem solving.

Causes and Treatments of Free Running Disorder

Researchers are still trying to figure out exactly why this sleep disorder occurs, but so far they speculate it’s related to light and darkness cues. It’s possible the brains of people with FRD don’t accurately process these cues, which can make it harder for the brain to determine appropriate times for sleeping and waking. (This helps explain why nearly 50 percent of people who are totally blind deal with a variation of FRD.)

Just as researchers are working to determine the causes of FRD, they’re also still uncertain as to whether there’s a cure. What we know so far is that several treatment options may assist people with managing the condition.

If you think you have FRD or any other sleep disorder, it’s best to consult a medical professional immediately. Treatments may include lifestyle changes (such as scheduling naps at opportune times, tweaking daily routines, and moderating exposure to sunlight), sound sleep habits (such as trying to sleep in a room that is cool, dark, and quiet, utilizing the bed for nothing but sleep, and so on), bright light therapy (to “jumpstart” a person’s body clock), and medications or supplementation with melatonin. While these treatments are not always successful, they may help people cope with the symptoms of FRD. Other people may find they’re simply happier adhering to the whims of their body’s abnormal circadian rhythms. If you think you have FRD or any other sleep disorder, it’s best to consult a medical professional immediately.