Absent cues from the environment, everyone’s circadian rhythm falls out of place. The brain’s suprachiasmatic nucleus keeps the master body clock, and in most people it is synchronized to the light of the day. Some people seem to not respond to this synchronization. Their internal clock becomes detached from nature’s and from most of human society’s. This condition is called free-running disorder. Also called non-entrained sleeping, free-running disorder often results in a steady drift of wake-up and sleep times. Over time the patient moves far out of the social norms for waking time, which can interfere with their lives.
Because they do not get light cues that most of us get, blind people are prone to free running disorder. It is estimated that over half of blind people have it. Sighted people can receive signals from the sunlight and their bodies adjust to natural daylight – sunrise and sunset.
The patient with free-running disorder often complains about insomnia and daytime sleepiness when he or she tries to conform to conventional sleep times. Teasing out non-entrained sleep patterns is not straightforward and may require some time and detective work. Actigraphy and sleep logs can help diagnose free-running disorder.
Is free-running disorder just an exaggerated version of advanced sleep-phase disorder or delayed sleep-phase disorder? It could be classified that way. The definitions of many sleep disorders overlap and there is always some subjective judgment in diagnosis. But the major sleep organizations do recognize free-running disorder as a separate category.
The word Asynchronization can refer to many things, including the phase being transposed and the amplitude or intensity of the circadian drive being off. There are always slight pushes off the synchronization train – jet lag, or a particularly late night, or unusual darkness in the morning. Feedback mechanisms in the normal person pushes the body’s cycle back on track – often at the expense of feeling bad or sleepy for a day or two.
Treatment for free running disorder is often behavioral. This means reminding patients to go to sleep and to get up at specified times, and building cues into their day that they will notice with their conscious brains even if their internal clock doesn’t respond to those cues. Long periods of time outdoors during the day may help, as can phototherapy. Exercise and meals can also help set the internal clock, and people with this disorder often do better by conscientiously following a planned and regular schedule for even routine daily tasks.
This is a disorder where melatonin is often the recommended drug therapy, especially for blind people. A large dose (say 10 mg) is given to help the patient get back on track and a maintenance dose of 0.5 mg/day is prescribed to keep the circadian cycle on target. With the recent introduction of the melatonin agonists ramelteon and tasimelteon, some doctors may prefer to use these medication instead, which have the advantage of being available in pharmaceutical grade purity and in measured doses, unlike health store melatonin which is not subject to as strict controls and likely to vary in quality and dosage.
The use of selective serotonin reuptake inhibitors has been investigated and serotonin levels do vary with the diurnal cycle so this idea has some merit, although it is less targeted than the use of melatonin agonists.