The Menstrual Cycle

Governed by monthly changes in hormone levels which regulate ovulation
Cycle refers to the time between the first day of a woman’s period to the day before her next one
The typical cycle takes approx. 28 days to complete
During each cycle, rising levels of the hormone oestrogen cause the ovary to develop an egg and release it (ovulation)
After ovulation, the hormone progesterone helps the womb lining grow thicker, readying the body for pregnancy
If pregnancy does not occur, the egg is absorbed into the body, the womb lining comes away and leaves the body

McClintock study

The menstrual cycle is usually controlled by an endogenous system - the release of hormones from the pituitary gland
However it can also be controlled by exogenous factors such as McClintock’s study shows
Samples of pheromones were gathered from 9 women at different stages of their menstrual cycle via a cotton pad placed in their armpit
The pads were rubbed on the upper lip of 20 participants
McClintock found that 68% of women experienced changes to their menstrual cycle which brought them closer to the cycle of their ‘odour donor’

SAD is a depressive disorder which has a season pattern
Similarly to other forms of depression, the main symptoms of SAD are persistent low mood, alongside lack of activity and interest in life
Often refereed to as winter blues, as the symptoms are triggered during winter months when the number of daylight hours becomes shorter
Psychologists predict that the hormone melatonin is linked to the cause of SAD
During the night, melatonin is secreted until dawn and then stops when there is increased daylight#
During winter, the lack of light in the morning means melatonin is secreted for longer
This has a knock on effect on the production of serotonin in the brain - a chemical that has been linked to the onset of depressive symptoms