infradian rhythms

• infradian rhythms

  Rhythms that take longer than a day to repeat.
• example: menstrual cycle

  -an infradian rhythm that lasts for approx one month

  -governed by changes in hormone levels

  -day 1: first day of menstration

  -increase oestrogen then increased progesterone

  -endogenous pacemakers: oestrogen & progesterone
• McClintok & Stern (1998)

  -29 women ppts, irregular periods

  -took samples of pheromones from 9 ppts at different points in the cycle

  -sanitised & froze the samples then put them on upper lip of ppts

  -68% of ppts had a changed cycle that matched the pheromones

  -shows exogenous zeitgebers are important in infradian rhythms
• Seasonal affective disorder (SAD)

  -main symptoms are like depression - influenced by melatonin produced in pineal gland

  -darker in the winter, produce melatonin for longer, impacts serotonin production (decreases)

  -happens in the winter, lasts all year (circannual cycle)

  -endogenous pacemakers: melatonin, pineal gland, serotonin
• AO3

  Strength(s):

  -research support. McClintok & Stern (1998). When women were presented with pheromones of other women on their cycle their cycle changed. Increases validity of exogenous factors on infradian rhythms. HOWEVER, in this research there were extraneous variables. Factors like stress or food can change the cycle/infradian rhythm. Decreases validity.

  -practical application. SAD: phototherapy reduces symptoms by 80%. Research into IR has use.