Currently, Non-24-Hour Sleep Wake Disorder (Non-24) is known to share symptoms that are similar to those found in other sleep disorders. Sleep patterns from previously recorded cases may give insight to certain signs to watch for. Although, recent work suggests that there is a large degree of variability of sleep complaints between individuals. Generally, the professional criteria suggest the presence of Non-24 if there is a complaint of cyclic insomnia and/or excessive daytime sleepiness, and that these abnormalities appear to be related to lack of synchronicity between the 24-hour day-night cycle and the internal body clock.
Non-24 patients sometimes complain of cyclic sleep problems; thus, individuals are able to enjoy episodes of good sleep. They can soon be followed, however, by episodes of poor sleep, then good sleep once again, and so on. The cyclic nature of Non-24 in some patients is one of the signs that separate Non-24 from other sleep disorders, although it is sometimes not easily recognized. Even total loss of vision does not necessarily eliminate the eye’s ability to send day-night signals to the SCN. In the totally visually blind, however, Non-24 should be suspected with complaints of cyclic sleep difficulties due to its prevalence in this group of people.
It is important to seek a specialized health professional for diagnosis of Non-24, as it has been misdiagnosed for other sleep deprivation or non-related psychiatric disorders in the past. The sleep specialist will generally discuss patient history and any medical documentation of sleep complaints. If a problem with the internal body clock is suspected, the doctor will ask the patient to keep a sleep diary for a few weeks and possibly months. As many patients will have already researched circadian rhythm disorders, they may often come prepared with a sleep log during the consultation. In addition, sleep-wake patterns can be obtained by using actigraphy, a non-invasive method of monitoring human rest and activity cycles. Here, rest-activity patterns are recorded using a device worn like a wristwatch to track movement. Sometimes, the sleep doctor may order an overnight polysomnogram (sleep study) to rule out other sleep disorders.
Not all patients will exhibit a clearly changing sleep-wake pattern. Particularly in blind patients, and ideally all patients, blood, saliva, or urine should be collected over several weeks to look for circadian biochemical chemical rhythms that can determine for sure whether the clock is exhibiting a non-24-hour rhythm. The sleep diaries and test results together will aid a sleep specialist in looking for patterns that demonstrate sleep and wake times that delay or advance daily with a period other than 24 hours.
Coping with Non-24-Hour Sleep Wake Disorder (Non-24) by forcing one’s self to keep a sleep schedule that matches the 24-hour day-night norm can lead to sleep deficits with symptoms that may mimic depression, and a possible misdiagnosis of Non-24 for a non-related psychiatric condition. Sleep deprivation itself, however, is a risk factor for depression, and can become an additional problem to manage alongside Non-24 (i.e., a co-morbidity) rather than a misdiagnosis.
As previously mentioned, Non-24 is caused by different mechanisms in blind and sighted individuals. For sighted subjects, several mechanisms for Non-24 have been suggested, including deficiencies in the ipRGC cells of the retina, under- or over-sensitivity of the eye to light, differences in the intrinsic circadian feedback loop, problems with melatonin production, etc. This is a serious disorder, extremely disruptive of people’s lives, and it is not known how many people suffer from it.
For totally blind patients, the disorder is caused by an inability of the circadian pacemaker to be synchronized to the 24-hour cycle by light due to the lack of a functional retina–retinohypothalamic tract–suprachiasmatic nuclei (RHT-SCN) pathway.
Non-24 can be considered intrinsic, physical, irreversible (but treatable) and not associated with any psychiatric condition in blind subjects. One previous study reported that of patients who had no psychiatric problems before the development of Non-24 symptoms, about a third developed major depression thereafter. In over a third of these depressed subjects, the symptoms of depression increased when they slept during the daytime and decreased slightly when they slept during the night. This observation suggests that the delay of sleep timing relative to the internal body clock may be an underlying cause of both Non-24 and co-morbid depression.
Correction of the delay of sleep timing may be important for the long-term treatment of both symptoms. It is very important to recognize psychiatric co-morbidities in Non-24 patients early because failure to do so may lead to unnecessary impairments in personal, academic, and family functioning at critical ages. For example, Non-24 is known to cause depression in the totally blind. When planning the initial phases of treatment, changes in sleep-focused psychiatric intervention are considered crucial for stabilizing mood and behavior. Both patients and their doctors should pay close attention to the stepwise patterns of co-morbid psychiatric disorders and Non-24 for early intervention.
Non 24-Hour Sleep Wake Disorder (Non-24) is often misdiagnosed as depression because symptoms of sleep deprivation often overlap with those of depression.
Feelings of hopelessness
People with Non-24 may feel misunderstood by their friends, co-workers, family members, and even their doctors because they do not understand why people with Non-24 cannot just re-program their body clocks to sleep on a normal schedule. People with Non-24 may also find it difficult, or even impossible, to maintain employment, keep appointments, care for their children, and maintain a social life. Things that require attention for long periods of time, such as watching a movie, going to a play or a sporting event, or sitting through a child’s concert, may also be difficult. These restrictions in day-to-day activities can contribute to feelings of depression. For people who are already suffering from depression, these impairments in daytime alertness and nighttime sleep can make their depression worse.
It’s important that people with Non-24 who also suffer from depression seek treatment. If left untreated, both sleep deprivation and depression can increase a person’s risk for chronic health problems, such as heart disease.