Pseudoscience Dictionary: Biorhythms

Pseudoscience: Consists of statements, beliefs, or practices that are claimed to be both scientific and factual but are incompatible with the scientific method (unproven, not testable, or opposed to the consensus of traditional science).

Biorhythms

Definition: Biorhythm theory is the belief that human physical, emotional, and intellectual abilities follow predictable cycles beginning at birth. According to the theory, physical performance follows a 23-day cycle, emotional stability a 28-day cycle, and intellectual ability a 33-day cycle. Proponents claim these cycles can predict periods of heightened performance, poor judgment, emotional difficulties, and increased accident risk. Particular emphasis is placed on so-called “critical days,” when an individual is supposedly more vulnerable to mistakes or misfortune.

Reasoning: Scientific research has consistently failed to support biorhythm theory. A comprehensive review published in Psychological Reports examined 134 studies, finding that 99 provided no support for the theory, while the remaining 35 contained methodological or statistical errors that explained their seemingly positive findings. The researcher concluded that biorhythm theory is invalid. Further, a study of aviation accidents involving more than 5,000 pilot-related cases found no relationship between accidents and supposedly critical biorhythm days. Similarly, research published in the Archives of General Psychiatry examined 205 highway crashes and found no evidence that biorhythm cycles predicted accident risk. Although legitimate biological rhythms, including circadian rhythms, influence sleep, alertness, and physiological functioning, these scientifically established processes do not validate the fixed 23-, 28-, and 33-day cycles proposed by biorhythm theory.

More Information

• Comprehensive Review of Biorhythm Theory – Psychological Reports
• No Evidence for Relationship Between Biorhythms and Industrial Accidents
• The Significance of Lunar Phases and Biorhythms in Trauma Patients

Conclusion: Biorhythm theory is pseudoscience. Extensive scientific testing has found no credible evidence that fixed cycles beginning at birth can predict physical performance, emotional well-being, intellectual ability, or accident risk. While biological rhythms are real, the specific claims of biorhythm theory lack scientific validity.

Last Updated on October 23, 2026 by Media Bias Fact Check

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