Which type of rhythm lasts longer than 24 hours and can include monthly cycles?

Infradian rhythms are characterized by cycles that last longer than 24 hours, which can include monthly or seasonal variations. A powerful example of an infradian rhythm is the menstrual cycle in humans, which typically lasts about 28 days. This type of rhythm allows organisms to synchronize their biological processes with longer-term environmental changes, such as those associated with the lunar cycle or seasonal variations.

Understanding infradian rhythms is important in the study of biology and psychology because they explain how certain behaviors and physiological processes are influenced by factors that change over extended periods. This contrasts with circadian rhythms, which follow a roughly 24-hour cycle, and ultradian rhythms, which repeat more frequently than daily. Diurnal rhythms are also related to the day-night cycle but specifically refer to activities that happen during the day versus night. Hence, infradian rhythms uniquely account for those longer cycles that can span days, weeks, or even months.