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Circadian Rhythm Resources

The academic literature on sleep and circadian biology is monsterous, but it represents the core sources the manual draws on, and gives you a starting point for going deeper into any specific area.

Where appropriate, citations include both the primary research and the practitioners or popularizers who’ve made that research accessible. Both have their place. Primary research is where the evidence actually lives. Popularizers and synthesizers are sometimes more accessible entry points, but should be cross-checked against the underlying papers.


Foundational Physiology and the Two-Process Model

  • Borbély, A.A. (1982). A two process model of sleep regulation. Human Neurobiology, 1(3), 195–204. The original framework. Borbély, A.A., Daan, S., Wirz-Justice, A., & Deboer, T. (2016). The two-process model of sleep regulation: a reappraisal. Journal of Sleep Research, 25(2), 131–143. 
  • Porkka-Heiskanen, T., Strecker, R.E., Thakkar, M., Bjørkum, A.A., Greene, R.W., & McCarley, R.W. (1997). Adenosine: a mediator of the sleep-inducing effects of prolonged wakefulness. Science, 276(5316), 1265–1268. The foundational paper on adenosine as the molecular substrate of Process S.
  • Saper, C.B., Scammell, T.E., & Lu, J. (2005). Hypothalamic regulation of sleep and circadian rhythms. Nature, 437(7063), 1257–1263. The flip-flop switch model of sleep-wake transitions.


The Suprachiasmatic Nucleus and Master Clock

  • Welsh, D.K., Takahashi, J.S., & Kay, S.A. (2010). Suprachiasmatic nucleus: cell autonomy and network properties. Annual Review of Physiology, 72, 551–577.
  • Berson, D.M., Dunn, F.A., & Takao, M. (2002). Phototransduction by retinal ganglion cells that set the circadian clock. Science, 295(5557), 1070–1073. The discovery of intrinsically photosensitive retinal ganglion cells (ipRGCs).
  • Foster, R.G. (2022). Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health. Penguin. The most rigorous popular treatment of circadian biology. Foster’s broader research output through the Sleep and Circadian Neuroscience Institute at Oxford is foundational.


Molecular Clock Genetics

  • Konopka, R.J., & Benzer, S. (1971). Clock mutants of Drosophila melanogaster. Proceedings of the National Academy of Sciences, 68(9), 2112–2116. The original Period gene work.
  • Vitaterna, M.H., King, D.P., Chang, A.M., Kornhauser, J.M., Lowrey, P.L., McDonald, J.D., Dove, W.F., Pinto, L.H., Turek, F.W., & Takahashi, J.S. (1994). Mutagenesis and mapping of a mouse gene, Clock, essential for circadian behavior. Science, 264(5159), 719–725. The CLOCK gene.


Sleep Architecture and Memory

  • Fogel, S.M., & Smith, C.T. (2011). The function of the sleep spindle: a physiological index of intelligence and a mechanism for sleep-dependent memory consolidation. Neuroscience and Biobehavioral Reviews, 35(5), 1154–1165.
  • Stickgold, R. (2005). Sleep-dependent memory consolidation. Nature, 437(7063), 1272–1278. Stickgold’s broader body of work on sleep and memory continues to be foundational.
  • Mander, B.A., Rao, V., Lu, B., Saletin, J.M., Lindquist, J.R., Ancoli-Israel, S., Jagust, W., & Walker, M.P. (2013). Prefrontal atrophy, disrupted NREM slow waves and impaired hippocampal-dependent memory in aging. Nature Neuroscience, 16(3), 357–364. Sleep architecture changes with aging.


Glymphatic Clearance

  • Iliff, J.J., Wang, M., Liao, Y., et al. (2012). A paravascular pathway facilitates CSF flow through the brain parenchyma and the clearance of interstitial solutes, including amyloid β. Science Translational Medicine, 4(147), 147ra111. The original glymphatic system paper from Maiken Nedergaard’s lab.
  • Xie, L., Kang, H., Xu, Q., et al. (2013). Sleep drives metabolite clearance from the adult brain. Science, 342(6156), 373–377. The follow-up linking glymphatic clearance specifically to sleep.
  • Lee, H., Xie, L., Yu, M., et al. (2015). The effect of body posture on brain glymphatic transport. Journal of Neuroscience, 35(31), 11034–11044. The lateral sleep position research.


Sleep Deprivation and Health Consequences

  • Van Dongen, H.P., Maislin, G., Mullington, J.M., & Dinges, D.F. (2003). The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation. Sleep, 26(2), 117–126. The foundational paper on sleep restriction blindness.
  • Buxton, O.M., Pavlova, M., Reid, E.W., Wang, W., Simonson, D.C., & Adler, G.K. (2010). Sleep restriction for 1 week reduces insulin sensitivity in healthy men. Diabetes, 59(9), 2126–2133.
  • Spiegel, K., Sheridan, J.F., & Van Cauter, E. (2002). Effect of sleep deprivation on response to immunization. JAMA, 288(12), 1471–1472.
  • Kripke, D.F., Garfinkel, L., Wingard, D.L., Klauber, M.R., & Marler, M.R. (2002). Mortality associated with sleep duration and insomnia. Archives of General Psychiatry, 59(2), 131–136. The contrarian mortality data.


Comparative and Anthropological Sleep

  • Yetish, G., Kaplan, H., Gurven, M., Wood, B., Pontzer, H., Manger, P.R., Wilson, C., McGregor, R., & Siegel, J.M. (2015). Natural sleep and its seasonal variations in three pre-industrial societies. Current Biology, 25(21), 2862–2868. The Hadza, San, and Tsimane sleep study from Jerome Siegel’s lab.
  • He, Y., Jones, C.R., Fujiki, N., Xu, Y., Guo, B., Holder, J.L., Rossner, M.J., Nishino, S., & Fu, Y.H. (2009). The transcriptional repressor DEC2 regulates sleep length in mammals. Science, 325(5942), 866–870. The DEC2 short-sleep gene.


Chronotypes and Social Jetlag

  • Roenneberg, T., Wirz-Justice, A., & Merrow, M. (2003). Life between clocks: daily temporal patterns of human chronotypes. Journal of Biological Rhythms, 18(1), 80–90. The Munich ChronoType Questionnaire foundation.
  • Wittmann, M., Dinich, J., Merrow, M., & Roenneberg, T. (2006). Social jetlag: misalignment of biological and social time. Chronobiology International, 23(1–2), 497–509.
  • Roenneberg, T., Kuehnle, T., Pramstaller, P.P., Ricken, J., Havel, M., Guth, A., & Merrow, M. (2004). A marker for the end of adolescence. Current Biology, 14(24), R1038–R1039. Adolescent chronotype shift.
  • Carskadon, M.A. (2011). Sleep in adolescents: the perfect storm. Pediatric Clinics of North America, 58(3), 637–647. Foundational adolescent sleep research underlying the AAP’s 2014 recommendation for later school start times.


Light, Melatonin, and Circadian Entrainment

  • Brainard, G.C., Hanifin, J.P., Greeson, J.M., Byrne, B., Glickman, G., Gerner, E., & Rollag, M.D. (2001). Action spectrum for melatonin regulation in humans: evidence for a novel circadian photoreceptor. Journal of Neuroscience, 21(16), 6405–6412. The melatonin suppression action spectrum.
  • Gooley, J.J., Chamberlain, K., Smith, K.A., Khalsa, S.B., Rajaratnam, S.M., Van Reen, E., Zeitzer, J.M., Czeisler, C.A., & Lockley, S.W. (2011). Exposure to room light before bedtime suppresses melatonin onset and shortens melatonin duration in humans. Journal of Clinical Endocrinology and Metabolism, 96(3), E463–E472.
  • Lewy, A.J., Ahmed, S., & Sack, R.L. (1996). Phase shifting the human circadian clock using melatonin. Behavioural Brain Research, 73(1–2), 131–134. Foundational melatonin phase-shifting research.
  • Hébert, M., Martin, S.K., Lee, C., & Eastman, C.I. (2002). The effects of prior light history on the suppression of melatonin by light in humans. Journal of Pineal Research, 33(4), 198–203.
  • Cho, C.H., Lee, H.J., Yoon, H.K., et al. (2016). Exposure to dim artificial light at night during sleep impairs sleep architecture and functional brain network connectivity. Chronobiology International, 33(1), 117–123.
  • Erland, L.A., & Saxena, P.K. (2017). Melatonin natural health products and supplements: presence of serotonin and significant variability of melatonin content. Journal of Clinical Sleep Medicine, 13(2), 275–281. The supplement quality control paper.
  • Rosenthal, N.E., Sack, D.A., Gillin, J.C., Lewy, A.J., Goodwin, F.K., Davenport, Y., Mueller, P.S., Newsome, D.A., & Wehr, T.A. (1984). Seasonal affective disorder: a description of the syndrome and preliminary findings with light therapy. Archives of General Psychiatry, 41(1), 72–80.


Sun Exposure, Vitamin D, and Skin Health

  • Lindqvist, P.G., Epstein, E., Nielsen, K., Landin-Olsson, M., Ingvar, C., & Olsson, H. (2016). Avoidance of sun exposure as a risk factor for major causes of death: a competing risk analysis of the Melanoma in Southern Sweden cohort. Journal of Internal Medicine, 280(4), 375–387. The Swedish cohort comparing aggressive sun avoidance to smoking.
  • Holick, M.F. (2007). Vitamin D deficiency. New England Journal of Medicine, 357(3), 266–281. Foundational vitamin D synthesis biology, with the caveat that Holick’s clinical recommendations and his financial relationships with the indoor tanning, supplement, and laboratory testing industries are documented in Szabo, L. (2018), The New York Times/Kaiser Health News investigation, and warrant a sceptical reading of his specific dose recommendations.
  • Manson, J.E., Cook, N.R., Lee, I.M., et al. (2019). Vitamin D supplements and prevention of cancer and cardiovascular disease. New England Journal of Medicine, 380(1), 33–44. The VITAL trial showing largely null results for hard endpoints.
  • Liu, D., Fernandez, B.O., Hamilton, A., Lang, N.N., Gallagher, J.M., Newby, D.E., Feelisch, M., & Weller, R.B. (2014). UVA irradiation of human skin vasodilates arterial vasculature and lowers blood pressure independently of nitric oxide synthase. Journal of Investigative Dermatology, 134(7), 1839–1846. Richard Weller’s UVA-and-cardiovascular work.
  • Clemens, T.L., Henderson, S.L., Adams, J.S., & Holick, M.F. (1982). Increased skin pigment reduces the capacity of skin to synthesise vitamin D3. Lancet, 1(8263), 74–76. The melanin-and-vitamin-D-synthesis relationship.
  • Hamblin, M.R. (2017). Mechanisms and applications of the anti-inflammatory effects of photobiomodulation. AIMS Biophysics, 4(3), 337–361. The foundational research on red and near-infrared light therapy.
  • Feldman, D., Pike, J., & Bouillon, R. (2019). Vitamin D (4th ed.). Academic Press. Standard academic textbook reference.


Time-Restricted Eating and Peripheral Clocks

  • Panda, S. (2018). The Circadian Code: Lose Weight, Supercharge Your Energy, and Transform Your Health from Morning to Midnight. Rodale Books. Panda’s primary research is published across multiple papers; the popular synthesis here is the most accessible entry point.
  • Manoogian, E.N.C., & Panda, S. (2017). Circadian rhythms, time-restricted feeding, and healthy aging. Ageing Research Reviews, 39, 59–67.


Insomnia, CBT-I, and Clinical Sleep Medicine

  • American Academy of Sleep Medicine. (2023). International Classification of Sleep Disorders (3rd ed., text revision).
  • Spielman, A.J., Caruso, L.S., & Glovinsky, P.B. (1987). A behavioral perspective on insomnia treatment. Psychiatric Clinics of North America, 10(4), 541–553. The 3-P model.
  • Qaseem, A., Kansagara, D., Forciea, M.A., Cooke, M., & Denberg, T.D. (2016). Management of chronic insomnia disorder in adults: a clinical practice guideline from the American College of Physicians. Annals of Internal Medicine, 165(2), 125–133.
  • Morin, C.M., Bootzin, R.R., Buysse, D.J., Edinger, J.D., Espie, C.A., & Lichstein, K.L. (2006). Psychological and behavioral treatment of insomnia: update of the recent evidence (1998–2004). Sleep, 29(11), 1398–1414.
  • van Straten, A., van der Zweerde, T., Kleiboer, A., Cuijpers, P., Morin, C.M., & Lancee, J. (2018). Cognitive and behavioral therapies in the treatment of insomnia: a meta-analysis. Sleep Medicine Reviews, 38, 3–16.
  • Espie, C.A., Kyle, S.D., Williams, C., Ong, J.C., Douglas, N.J., Hames, P., & Brown, J.S. (2012). A randomized, placebo-controlled trial of online cognitive behavioral therapy for chronic insomnia disorder delivered via an automated media-rich web application. Sleep, 35(6), 769–781. The Sleepio digital CBT-I research.
  • Koffel, E., Bramoweth, A.D., & Ulmer, C.S. (2018). Increasing access to and utilization of cognitive behavioral therapy for insomnia (CBT-I): a narrative review. Journal of General Internal Medicine, 33(6), 955–962. The CBT-I underuse documentation.


Sleep Medications and Pharmacology

  • American Geriatrics Society Beers Criteria Update Expert Panel. (2019). American Geriatrics Society 2019 updated AGS Beers Criteria for potentially inappropriate medication use in older adults. Journal of the American Geriatrics Society, 67(4), 674–694.
  • U.S. Food and Drug Administration. (2019). FDA adds boxed warning for risk of serious injuries caused by sleepwalking with certain prescription insomnia medicines.
  • Coupland, C.A.C., Hill, T., Dening, T., Morriss, R., Moore, M., & Hippisley-Cox, J. (2019). Anticholinergic drug exposure and the risk of dementia: a nested case-control study. JAMA Internal Medicine, 179(8), 1084–1093.


Sleep Apnea and Sleep-Disordered Breathing

  • Senaratna, C.V., Perret, J.L., Lodge, C.J., Lowe, A.J., Campbell, B.E., Matheson, M.C., Hamilton, G.S., & Dharmage, S.C. (2017). Prevalence of obstructive sleep apnea in the general population: a systematic review. Sleep Medicine Reviews, 34, 70–81.
  • McEvoy, R.D., Antic, N.A., Heeley, E., et al. (2016). CPAP for prevention of cardiovascular events in obstructive sleep apnea. New England Journal of Medicine, 375(10), 919–931. The SAVE trial.


Other Sleep Disorders

  • Lin, L., Faraco, J., Li, R., Kadotani, H., Rogers, W., Lin, X., Qiu, X., de Jong, P.J., Nishino, S., & Mignot, E. (1999). The sleep disorder canine narcolepsy is caused by a mutation in the hypocretin (orexin) receptor 2 gene. Cell, 98(3), 365–376. Mignot’s foundational narcolepsy work.
  • Postuma, R.B., Iranzo, A., Hu, M., et al. (2019). Risk and predictors of dementia and parkinsonism in idiopathic REM sleep behaviour disorder: a multicentre study. Brain, 142(3), 744–759. RBD as predictor of neurodegenerative disease.
  • International Agency for Research on Cancer. (2007). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 98: Painting, Firefighting, and Shiftwork. Shift work classification.


Sleep Environment

  • Strøm-Tejsen, P., Zukowska, D., Wargocki, P., & Wyon, D.P. (2016). The effects of bedroom air quality on sleep and next-day performance. Indoor Air, 26(5), 679–686.
  • Haghayegh, S., Khoshnevis, S., Smolensky, M.H., Diller, K.R., & Castriotta, R.J. (2019). Before-bedtime passive body heating by warm shower or bath to improve sleep: a systematic review and meta-analysis. Sleep Medicine Reviews, 46, 124–135.


Exercise, Food, and Supplements for Sleep

  • Kredlow, M.A., Capozzoli, M.C., Hearon, B.A., Calkins, A.W., & Otto, M.W. (2015). The effects of physical activity on sleep: a meta-analytic review. Journal of Behavioral Medicine, 38(3), 427–449.
  • Kovacevic, A., Mavros, Y., Heisz, J.J., & Fiatarone Singh, M.A. (2018). The effect of resistance exercise on sleep: a systematic review of randomized controlled trials. Sleep Medicine Reviews, 39, 52–68.
  • Howatson, G., Bell, P.G., Tallent, J., Middleton, B., McHugh, M.P., & Ellis, J. (2012). Effect of tart cherry juice (Prunus cerasus) on melatonin levels and enhanced sleep quality. European Journal of Nutrition, 51(8), 909–916.
  • Lin, H.H., Tsai, P.S., Fang, S.C., & Liu, J.F. (2011). Effect of kiwifruit consumption on sleep quality in adults with sleep problems. Asia Pacific Journal of Clinical Nutrition, 20(2), 169–174.
  • Abbasi, B., Kimiagar, M., Sadeghniiat, K., Shirazi, M.M., Hedayati, M., & Rashidkhani, B. (2012). The effect of magnesium supplementation on primary insomnia in elderly: a double-blind placebo-controlled clinical trial. Journal of Research in Medical Sciences, 17(12), 1161–1169.
  • Hidese, S., Ogawa, S., Ota, M., Ishida, I., Yasukawa, Z., Ozeki, M., & Kunugi, H. (2019). Effects of L-theanine administration on stress-related symptoms and cognitive functions in healthy adults: a randomized controlled trial. Nutrients, 11(10), 2362.


Sleep Tracking and Wearable Validity

  • de Zambotti, M., Cellini, N., Goldstone, A., Colrain, I.M., & Baker, F.C. (2019). Wearable sleep technology in clinical and research settings. Medicine and Science in Sports and Exercise, 51(7), 1538–1557.
  • Baron, K.G., Abbott, S., Jao, N., Manalo, N., & Mullen, R. (2017). Orthosomnia: are some patients taking the quantified self too far? Journal of Clinical Sleep Medicine, 13(2), 351–354.


Books and Practitioner Sources

  • Walker, M. (2017). Why We Sleep: Unlocking the Power of Sleep and Dreams. Simon and Schuster. The most-read popular sleep book ever written. Read alongside Guzey, A. (2019), “Matthew Walker’s Why We Sleep is riddled with scientific and factual errors,” available through Guzey’s archive. Walker’s broader framework is largely correct directionally; specific quantitative claims should be checked against the original literature.
  • Foster, R.G. (2022). Life Time: The New Science of the Body Clock, and How It Can Revolutionize Your Sleep and Health. Penguin. The most rigorous popular treatment of circadian biology currently available.
  • Stanley, N. (2018). How to Sleep Well. Capstone. Stanley is a UK sleep researcher; his treatment is more grounded than most popular sleep books.
  • Winter, W.C. (2017). The Sleep Solution: Why Your Sleep is Broken and How to Fix It. Penguin. Winter is a sleep medicine physician; useful clinical perspective.
  • Breus, M. (2016). The Power of When: Discover Your Chronotype and Maximize Your Potential. Random House. The four-animal chronotype taxonomy. Pedagogically useful as starting points; not scientifically validated as discrete categories. Use loosely rather than as fixed identity classification. Roenneberg’s continuous-distribution framework (cited above) is the better-grounded alternative.
  • Greenfield, B. (2020). Boundless: Upgrade Your Brain, Optimize Your Body and Defy Aging. Victory Belt Publishing. The biohacker comprehensive treatment. Some recommendations are well-supported, many are speculative or commercially motivated. Useful as a survey of practitioner-level interventions; cross-check specific claims against primary research.
  • Sovijärvi, O., Arina, T., & Halmetoja, J. (2019). Biohacker’s Handbook. Biohacker Center. Finnish biohacker community treatment. Similar caveats to Greenfield: useful breadth of practical interventions, with claims that should be checked against primary research.
  • Asprey, D. (2019). Super Human. Newbury House Publishers. Founder of the modern biohacker movement. Read with appropriate scepticism; some content is grounded, some is commercially motivated, some is essentially marketing for products Asprey sells.


Practitioners and Online Resources

  • Foster, R.G.: Sleep and Circadian Neuroscience Institute, Oxford. Foster’s research output and his public communication continue to set the standard for rigor in this space.
  • Czeisler, C.: Division of Sleep and Circadian Disorders, Brigham and Women’s Hospital, Harvard Medical School. Foundational research on light, melatonin, and clinical sleep medicine.
  • Panda, S.: Salk Institute. Time-restricted eating and peripheral circadian clock research.
  • Walker, M.: Center for Human Sleep Science, UC Berkeley. With caveats noted above regarding Why We Sleep.
  • Huberman Lab podcast: hubermanlab.com. Andrew Huberman is a primary researcher (Stanford ophthalmology and neuroscience) as well as a popularizer. Useful synthesis of sleep and circadian science; specific protocol recommendations sometimes outrun the underlying research and warrant cross-checking.
  • Patrick, R.: FoundMyFitness, foundmyfitness.com. Useful synthesis of nutritional and physiological topics including vitamin D. The Vitamin D topic page at foundmyfitness.com/topics/vitamin-d is a comprehensive entry point.