Ultradian

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Ultradian rhythms are recurrent periods or cycles repeated throughout a 24-hour circadian day. (In contrast, infradian rhythms have periods longer than a day, for example the human menstrual cycle.)

The descriptive term ultradian is used in sleep research in reference to the 90-110 minute cycling of the sleep stages during human sleep.

Some of the other ultradian cyclings of the body are hormonal release, heart rate, thermoregulation, urination, bowel activity, nostril dilation and appetite. The last involves rhythmic release of Neuropeptide Y (NPY) and Corticotropin-releasing hormone (CRH), stimulating and inhibiting appetite ultradian rhythms.

Ultradian states in bipolar disorder cycle much faster than rapid cycling, which is defined as four or more mood episodes in one year, sometimes occurring within a few weeks. Ultradian mood cycling is characterized by cycles shorter than 24 hours.

[edit] References

• Ultra-rapid and ultradian cycling in bipolar affective illness. Kramlinger KG, Post RM. Br J Psychiatry. 1996 Mar;168(3):314-23. Associated Articles and Links [1]