Infradian & Ultradian Rhythm

  • Created by: ritig23
  • Created on: 01-07-17 18:31

Infradian Rhythm:

·         Type of biological rhythm

·         With a frequency of less than one cycle in 24 hours

·         Such as menstruation and seasonal affective disorder

Ultradian Rhythm:

·         Type of biological rhythm

·         Frequency of more than one cycle in 24 hours, e.g. stages of sleep


Infradian Rhythms:

The menstrual cycle:

The female menstrual cycle is governed by monthly changes in hormone levels which regulate ovulation. The cycle refers to the time between the first day of a woman’s period, when the womb lining is shed, to the day before her next period. The typical cycle take approximately 8 days to complete. During each cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it. After ovulation, the hormone progesterone helps the womb lining to grow thicker, readying the body for pregnancy.

Research study:

The menstrual cycle is an endogenous system; however evidence suggests that it may be influenced by exogenous factors, such as the cycles of other woman. McClintock (1988) demonstrated how menstrual cycles may synchronise as a result of the influence of female pheromones. The findings show that 68% of woman experienced changes to their cycle which brought them closer to the cycle of their ‘odour donor’.

Seasonal affective disorder (SAD):

SAD is a depressive disorder which has a seasonal pattern of onset, and is described and diagnosed as a mental disorder in DSM-5. The main symptoms include: persistent low mood alongside a general lack of activity and interest in life. The symptoms are triggered during winter months when the numbers of daylight hours have become shorter. SAD is a particular type of infradian rhythm called a circadian rhythm as the experience of SAD may be due…


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