infradian ryhtyms

• what are Infradian rhythms?

  rhythms that last longer than 24 hours and can be weekly monthly or even annually
• 1. A monthly infradian rhythm is the female menstrual cycle, which is regulated by hormones that promote ovulation or stimulate the uterus for fertilisation. 
  2. Halfway through the cycle is ovulation - oestrogen levels are highest, (lasts for 16-32 hours). 
  3. After the ovulatory phase, progesterone levels increase in preparation for the possible implantation of an embryo in the uterus. 
  4. Normal cycle lasts 28 days, there cqn be variation, so a cycle of 23 days and others cycles up to 36 days.
• seasonal affective disorder 

  • Research has found seasonal variation in mood, 
  • SAD is an infradian rhythm on a yearly cycle. 
  • Psychologists claim The lack of light and longer nights during the winter months results in a longer period of melatonin secretion by the pineal gland which has been linked to the depressive symptoms.
  • Most deaths occurring in january
• (knowledge about infradina rythms applied to understanding the behaviour of Women. Evidence to suggest that infradian rhythms are also important regulators of behaviour,penton volk eg al  found that women expresseda preference for feminised faces at the least fertile stage  and for a more masculine face at the most fertile point. Thes findinings indicate that womnes sexual behaviour is motivated by their infradian rhytms highlighting the importance in studying ryythms in relation to human behaviour)
• THis Research suggests, the menstrual cycle is usually governed by and endogenous system of hormones released by gland, however other reserach suggests ez also play a role.

  • Reinberg -woman in a cave for 3 months (small lamp).
  • cycle shortened - 28 days to 25.7 days. no light affected cycle = role of external factors.
  • Further evidence is women of chilbering age live together (no take oral contraceptives) their cycles synchronise
  • Russell applied daily sweat samples from one group of women to the upper lip of others and synchronised,
  • women's menstrual cycle can be regulated by pheromones from other women (ezs).
• • Support for SAD
  • Terman found that the rate of depression is higher in northern countries where winter nights are longer where winter nights are longer 
  • affects 10 perent in new hampshire (northern) and only 2 percent in florida- 
  • SHows research support for the existence of this diisorder and suggests infradian rhythms are affected by exogenous zeitbeigers like light - however it is only correlational as there is no objective way in measuring a cause and effect relationship between light levels and depresion, there other external factors other than light contributing towards depressive sysmpomts- individual differences som epoeple may have more difficulties in their general life not to do with light levels. Whilst it can be a contributing factor it may not be the only one.