Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 3 complete abstracts (672 words), 9 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
The tendency of a phenomenon to recur at regular intervals; in biological systems, the recurrence of certain activities (including hormonal, cellular, neural) may be annual, seasonal, monthly, daily, or more frequently (ultradian).
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Periodicities; Biorhythms; Biorhythm; Bioperiodicity; Bioperiodicities; Biological Rhythms; Biological Rhythm; Rhythm, Biological.
Where it fits in the MeSH classification
- Broader topics
- Time; Chronobiology Phenomena
- Narrower topics
- Seasons; Biological Clocks; Circadian Rhythm; Infradian Rhythm; Ultradian Rhythm
Research landscape
PubMed indexes 245,291 records tagged with the MeSH heading “Periodicity” (counts retrieved 2026-10-31). 44,136 of them (18.0%) were published from 2020 onward, and the busiest period so far is through 1999 with 81,236 records.
Reviews account for 17,589 records (7.2%) and meta-analyses for 669. Randomized controlled trials number 4,117 (1.7%) as a share of all records on the topic. Randomized trials make up only a small share of this literature, so much of what is known comes from laboratory, observational or descriptive work.
Show the data
| Period | Records |
|---|---|
| through 1999 | 81,236 |
| 2000-2009 | 51,783 |
| 2010-2019 | 68,136 |
| 2020 onward | 44,136 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 17,589 | 7.2% |
| Meta-analyses | 669 | 0.3% |
| Randomized controlled trials | 4,117 | 1.7% |
Method: PubMed query "Periodicity"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in anatomy and physiology
Anatomy describes how body structures are built and physiology describes how they normally work, so most findings here are descriptive or mechanistic rather than evidence about treatment. Much of what is known comes from dissection, imaging, tissue studies and experiments in animals, and measurements in healthy volunteers can differ from those in people with disease or at different ages. Normal ranges vary between individuals and populations. Check whether a result was measured in people or in another species, the age and health of the participants, and the method used.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
| Study / authors | Year | Source label / design | Europe PMC citations | Licence / source |
|---|---|---|---|---|
| mTOR signaling contributes to system-driven rhythmic gene expression in mouse liver | 2026 | Research article Design not recorded in structured metadata | 2 | cc by PMID 42490445 · DOI · PMC13394481 |
| Polyrhythm Perception and Production: A Scoping Review | 2026 | Research article Design not recorded in structured metadata | 2 | cc by PMID 42376933 · DOI · PMC13316977 |
| Impact of Δ9-tetrahydrocannabinol and oxycodone coadministration on measures of antinociception, dependence, circadian activity, and reward in mice | 2026 | Research article Design not recorded in structured metadata | 1 | cc by PMID 42685513 · DOI · PMC13688984 |
mTOR signaling contributes to system-driven rhythmic gene expression in mouse liver [1]
Abstract reading summary — source excerpts
- Opening excerpt
- Rhythmic gene expression is essential to the daily organization of biological processes.
- Closing excerpt
- These findings may explain how misalignment between clock and systemic signals contributes to disease and underscore the use of mTOR inhibitors for resynchronizing system-driven rhythms and alleviating circadian rhythm disorders.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (154 words)
Rhythmic gene expression is essential to the daily organization of biological processes. While cycling transcriptomes are regulated by circadian clocks present in nearly every cell, accumulating evidence indicates that they can also be initiated by rhythmic food-driven systemic signals independently of circadian clocks. The underlying mechanisms remain however largely unknown. Here, we show that signaling through the nutrient-sensing kinase mechanistic target of rapamycin (mTOR) is both necessary and sufficient to mediate food-driven hepatic rhythmic gene expression, rhythmic regulation of the liver metabolome, and endoplasmic reticulum stress response. Acute inhibition of mTOR before the active phase desynchronizes the phase of mTOR-driven rhythmic genes without affecting clock-controlled rhythmic genes, indicating that alignment of rhythmic mTOR activity to the circadian cycle is critical for overt cycling transcriptomes. These findings may explain how misalignment between clock and systemic signals contributes to disease and underscore the use of mTOR inhibitors for resynchronizing system-driven rhythms and alleviating circadian rhythm disorders.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42490445 · DOI · PMC13394481
Polyrhythm Perception and Production: A Scoping Review [2]
Abstract reading summary — source excerpts
- Opening excerpt
- In music, rhythms can range from simple isochrony to complex polyrhythms, in which multiple nonharmonically related metrical hierarchies are superimposed (e.
- Closing excerpt
- Combining behavioral and subjective measures across different polyrhythmic contexts could clarify subjective complexity and under which circumstances polyrhythms are perceived and produced as integrated rhythms or segregated pulses.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (199 words)
In music, rhythms can range from simple isochrony to complex polyrhythms, in which multiple nonharmonically related metrical hierarchies are superimposed (e.g., 2:3, 4:5). This scoping review synthesizes 64 studies comprising 96 experiments on polyrhythm perception and production. Over the past decades, research has shown that factors such as polyrhythm ratio, tempo, sensory modality, and musical training shape how we perceive and produce polyrhythms. Although most reviewed studies lack subjective measurements of polyrhythm complexity, behavioral tasks suggest that ratio sum (e.g., five in 2:3) and the Farey tree offer rough complexity estimates. While tempo affects which periodicity is perceived as the underlying beat, these effects are limited by the preference for binary subdivision grouping. Finally, the reviewed literature suggests that polyrhythms are more often perceived as integrated patterns than segregated streams. For future research, we recommend defining polyrhythms as the superposition of two or more nonharmonically related pulses that share a common cycle, and adding a clear description of whether these pulses are isochronous stimuli or perceived beats extracted from nonisochronous stimuli. Combining behavioral and subjective measures across different polyrhythmic contexts could clarify subjective complexity and under which circumstances polyrhythms are perceived and produced as integrated rhythms or segregated pulses.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42376933 · DOI · PMC13316977
Impact of Δ9-tetrahydrocannabinol and oxycodone coadministration on measures of antinociception, dependence, circadian activity, and reward in mice [3]
Abstract reading summary — source excerpts
- Opening excerpt
- Oxycodone is commonly prescribed for moderate-to-severe pain.
- Closing excerpt
- The increased abuse liability of such combinations is a primary consideration for their therapeutic evaluation.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (319 words)
Oxycodone is commonly prescribed for moderate-to-severe pain. While efficacious, long-term use can result in tolerance, physical dependence, and opioid use disorder. Cannabis and Δ9-tetrahydrocannabinol (Δ9-THC) have been reported to potentiate oxycodone-induced antinociception in animals and humans. Whether Δ9-THC also facilitates unwanted aspects of oxycodone intake, such as tolerance, dependence, and reward at antinociceptive doses, remains unclear. We evaluated the coadministration of Δ9-THC and oxycodone on antinociception, dependence, circadian activity, and reward in male and female mice. Oxycodone and Δ9-THC produced dose-dependent antinociception in the hotplate assay, with oxycodone showing lower potency in females. Repeated treatment (twice daily for 5 days) produced antinociceptive tolerance. Δ9-THC produced a potentiation-like effect on oxycodone-induced antinociception and delayed antinociceptive tolerance. Repeated oxycodone produced physical dependence and alterations in circadian activity, neither of which was exacerbated by cotreatment with Δ9-THC. Combination treatment of oxycodone and Δ9-THC produced conditioned place preference at doses that did not produce preference when administered alone. Fiber photometry recordings of nucleus accumbens dopamine release showed that Δ9-THC potentiated oxycodone-evoked dopamine release at subeffective oxycodone doses, a candidate mechanism for the behavioral reward potentiation. These data indicate that Δ9-THC may facilitate oxycodone-induced antinociception without augmenting certain unwanted features of opioid intake (eg, dependence and circadian rhythm alterations). However, Δ9-THC also recruited the rewarding properties of oxycodone at therapeutically relevant doses. These reward-related findings indicate that Δ9-THC and oxycodone combinations may carry increased abuse liability, a primary consideration for their therapeutic evaluation. SIGNIFICANCE STATEMENT: In mice, Δ9-tetrahydrocannabinol (Δ9-THC) produced a potentiation-like effect on oxycodone-induced antinociception and delayed antinociceptive tolerance without exacerbating opioid dependence or circadian disruption, but Δ9-THC also produced conditioned place preference and potentiated nucleus accumbens dopamine release at subeffective oxycodone doses. These findings indicate that Δ9-THC may enhance oxycodone-induced antinociception, but also that Δ9-THC recruits the rewarding properties of oxycodone at doses that are otherwise subeffective. The increased abuse liability of such combinations is a primary consideration for their therapeutic evaluation.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 42685513 · DOI · PMC13688984
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis [4]
- Research article Diurnal cortisol slopes and mental and physical health outcomes: A systematic review and meta-analysis [5]
- Research article The characteristics of persistent sexual offenders: a meta-analysis of recidivism studies [6]
- Research article Air pollution and daily mortality: a review and meta analysis [7]
- Research article Reference values for the five-repetition sit-to-stand test: a descriptive meta-analysis of data from elders [8]
- Research article Meta-analysis of the morning excess of acute myocardial infarction and sudden cardiac death [9]
References
- Sahasrabudhe A, Guy CR, Jacq A, Ho CW, Greenwell BJ, Menet JS. mTOR signaling contributes to system-driven rhythmic gene expression in mouse liver. . 2026. PMID 42490445 · DOI · PMC13394481
- Nijhuis P, Møller C, Bamford JS, Stupacher J. Polyrhythm Perception and Production: A Scoping Review. . 2026. PMID 42376933 · DOI · PMC13316977
- Slivicki RA, Wang JG, Kucz KV, Hines JF, Tran Nhat VT, Kravitz AV, et al.. Impact of Δ9-tetrahydrocannabinol and oxycodone coadministration on measures of antinociception, dependence, circadian activity, and reward in mice. . 2026. PMID 42685513 · DOI · PMC13688984
- Nair H, Brooks WA, Katz M, Roca A, Berkley JA, Madhi SA, et al.. Global burden of respiratory infections due to seasonal influenza in young children: a systematic review and meta-analysis. Lancet. 2011. PMID 22078723 · DOI
- Adam EK, Quinn ME, Tavernier R, McQuillan MT, Dahlke KA, Gilbert KE. Diurnal cortisol slopes and mental and physical health outcomes: A systematic review and meta-analysis. Psychoneuroendocrinology. 2017. PMID 28578301 · DOI · PMC5568897
- Hanson RK, Morton-Bourgon KE. The characteristics of persistent sexual offenders: a meta-analysis of recidivism studies. J Consult Clin Psychol. 2005. PMID 16392988 · DOI
- Schwartz J. Air pollution and daily mortality: a review and meta analysis. Environ Res. 1994. PMID 8287841 · DOI
- Bohannon RW. Reference values for the five-repetition sit-to-stand test: a descriptive meta-analysis of data from elders. Percept Mot Skills. 2006. PMID 17037663 · DOI
- Cohen MC, Rohtla KM, Lavery CE, Muller JE, Mittleman MA. Meta-analysis of the morning excess of acute myocardial infarction and sudden cardiac death. Am J Cardiol. 1997. PMID 9185643 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.