Infradian Rhythms

• What is an infradian rhythm?

  Biological rhythm lasting longer than 24 hours
• What is an example of a monthly infradian rhythm?

  The female menstrual cycle
• What happens to progesterone levels after ovulation?

  They increase in preparation for implantation
• What is the usual length of the menstrual cycle?

  Around 28 days
• What is a notable variation in menstrual cycle length?

  Some women have cycles of 23 to 36 days
• What is seasonal affective disorder (SAD)?

  Depression related to seasonal changes
• What governs the infradian rhythm of SAD?

  A yearly cycle
• What role does melatonin play in SAD?

  It is partly responsible for depressive symptoms
• How does light exposure affect melatonin secretion in winter?

  Less light leads to longer melatonin secretion
• What did Reinberg's study in 1967 demonstrate?

  Lack of light affects menstrual cycle length
• What did Russell et al. (1980) find about menstrual cycles?

  They can synchronize through odour exposure
• What do pheromones do in relation to menstrual cycles?

  They affect nearby individuals' cycles
• What do evolutionary psychologists claim about synchronized menstrual cycles?

  They provide an evolutionary advantage for childcare
• What did Penton-Volk et al. (1999) discover about women's preferences?

  Preferences for faces change with fertility
• What did Terman (1988) find about SAD rates in different regions?

  SAD is more common in Northern countries
• What percentage of people in New Hampshire are affected by SAD?

  About 10%
• What percentage of people in southern Florida are affected by SAD?

  About 2%
• How does light exposure relate to SAD and melatonin levels?

  Light affects melatonin levels and SAD rates
• What are the durations of infradian rhythms?

  They can be weekly, monthly, or annually
• How does the menstrual cycle relate to hormones?

  It is regulated by hormones promoting ovulation
• What is the duration of ovulation?

  16-32 hours
• How does seasonal variation relate to infradian rhythms?

  It can lead to conditions like SAD
• What is the significance of exogenous zeitgebers?

  They can influence infradian rhythms
• What is suggested for studying infradian rhythms?

  A holistic approach should be taken
• What advantage does synchronized menstrual cycles provide?

  Shared childcare among mothers
• How do infradian rhythms affect sexual preferences?

  They influence preferences for different face types
• What is the relationship between SAD and light exposure?

  Light exposure affects melatonin and SAD