Ecology Biological Rhythms
Roberto Refinetti
  • LAST REVIEWED: 25 July 2023
  • LAST MODIFIED: 25 July 2023
  • DOI: 10.1093/obo/9780199830060-0246


Biological rhythms are oscillatory processes observed in living beings—while the beings are alive or even after their death, as is the case for populational oscillations determined by the study of geological cycles using fossilized organisms. Until life on other planets can be documented, biological rhythms are considered to be restricted to organisms on planet Earth. The most obvious separation between types of biological rhythms is the one between rhythms that are purely caused by environmental cycles on one hand and rhythms that are generated endogenously and are only modulated by environmental cycles on the other hand. Technically, the term “circa” should be used only for rhythms that have been demonstrated to be endogenously generated and to be susceptible to synchronization by environmental cycles, which as of today applies only to circatidal, circalunar, circadian, and circannual rhythms. However, there are many other oscillatory patterns that have been observed in living organisms, and they are undoubtedly biological rhythms even if many of them may not be controlled by biological clocks. Biological rhythms are usually classified into three main categories: those that oscillate about once a day (circadian), those that oscillate faster than once a day (ultradian), and those that oscillate slower than once a day (infradian). Bibliographies in these three categories will be detailed below, after a brief discussion of professional journals and considerations about the reliability of oscillations presumed to constitute biological rhythms.

Specialized Journals

Research on biological rhythms is published in a variety of journals in many scientific disciplines, but there are a few journals that are focused specifically on biological rhythms. Biological Rhythm Research and the Journal of Biological Rhythms publish primarily basic research articles, with more rigorous studies in the latter than in the former. Chronobiology International publishes primarily practical and medical articles, often dealing with shift work and chronotherapy. The Journal of Circadian Rhythms publishes very few articles in various topics related to circadian rhythms. Sleep and Biological Rhythms publishes articles almost exclusively about sleep, rarely covering other types of biological rhythms. There are also many journals entirely dedicated only to sleep, but they are not listed here, as they focus primarily on the restorative component of sleep rather than on its circadian component.

  • Biological Rhythm Research.

    Impact factor: 1.362. Covers all aspects of research into the broad topic of biological rhythms. The areas covered can range from studies at the genetic or molecular level to those of behavioral or clinical topics. It can also include ultradian, circadian, infradian, or annual rhythms.

  • Chronobiology International.

    Impact factor: 3.749. A transdisciplinary journal focusing on biological rhythm phenomena of all life forms. Articles pertain to basic and applied chronobiology, and to methods, statistics, and instrumentation for biological rhythm study.

  • Journal of Biological Rhythms.

    Impact factor: 3.649. Articles describe original research in all aspects of biological rhythms, using genetic, biochemical, physiological, behavioral, epidemiological, and modeling approaches, as well as clinical trials. Emphasis is on circadian and seasonal rhythms.

  • Journal of Circadian Rhythms.

    Impact factor: 2.400. An open access online journal that publishes research articles dealing with circadian and nycthemeral (daily) rhythms in living organisms, including processes associated with photoperiodism and daily torpor.

  • Sleep and Biological Rhythms.

    Impact factor: 1.390. Publishes original articles, short papers, commentaries, and reviews. Covers mechanisms of sleep and wakefulness from the ranging perspectives of basic science, medicine, dentistry, pharmacology, psychology, engineering, public health, and social sciences.

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