Scientists who have undertaken a series of studies have determined that there is a direct and measurable link between hair growth cycles and circadian rhythms.
Chronobiology is the study of circadian rhythms.
Humans fall into three types of circadian rhythm patterns.
The types are tied to what time of day humans are more awake and alert in a 24-hour cycle.
Humans with early circadian rhythms are known as larks while later ones are known as owls. The third group of individuals is intermediate.
According to NIH.Gov circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle.
These natural processes respond primarily to light and dark.
They affect most living things, including humans, animals, plants, and microbes.
Once hair growth has passed from the anagen phase, clock genes express themselves in the hair cells at the bottom of the hair follicle.
Note: The three stages of hair growth are the anagen, catagen, and telogen phases.
The circadian clock differs among the phases of the hair growth cycle.
The circadian clock can adjust how the hair stem cells are turned off or on, which controls the hair growth cycles.
Through a clock gene called BMAL1, stem cell genes can be affected to become more or less active.
Mutations might occur in the clock genes. This might include the deletion of BMAL1. Stem cells may become inactive and lead to diminished hair growth. 
The circadian clock can adjust how the hair stem cells are turned off or on, which controls the entire hair growth cycle.
Results of the study indicate that sleep deprivation affects the circadian rhythm which may affect hair growth cycles.
Will getting more sleep every night trigger the growth of long and lusher hair?
There is good evidence that the hair follicle has a biological clock and may be directly connected to the body’s circadian rhythm.
PER1 and BMAL1 are potential targets for therapy in modulating hair growth by avoiding undesired effects on the central clock.
By blocking the activity of such genes, future therapies may prevent hair loss (alopecia).
By promoting the activity of these target genes, therapy may suppress unwanted hair growth (hirsutism).
Melatonin regulates the sleep-wake cycles. It may influence the hair growth cycle. 
Topical application of melatonin may be a treatment option for those with female and male pattern hair loss which may become available in the future.
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 Al-Nuaimi Y, Hardman JA, Biro T, et al. A meeting of two chronobiological systems: circadian proteins Period1 and BMAL1 modulate the human hair cycle clock. J Invest Dermatol.2014;134(3):610-619; PMID: 24005054
 Fischer TW, Trüeb RM, Hänggi G, et al. Topical Melatonin for Treatment of Androgenetic Alopecia. Int J Trichology.2012;4(4):236-245; PMID: 23766606Disclaimer: The information provided above is for entertainment purposes. Do not use this information as a substitute for medical advice.
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