Infradian rhythms Flashcards
What is an infradian rhythm?
Infradian rhythms last longer than 24 hours and can be weekly, monthly or annually.
Give an example of an infradian rhythm?
the female mestrual cycle: governed by monthly changes in hormone levels which regulate ovulation
Describe a study that has explored an infradian rhythm.
McClintock and Stern 1998 - investigated whether the menstrual cycle is influenced by pheremonal secretions from other women, 29 female university students (not taking birth control pills), 20 were exposed to pheromones, experimental group cycle became shorter, synchornisation of cycles’
What are the methodological limitations of this study?
confounding variables e.g. stress, changes in diet, exercises. lack internal validity, lack of control
Evaluate an evolutionary perspective on this study.
human response to pheromones is not yet well understood, and the precise substance involved in the mechanism by which it affects the menstrual cycle. evolutionary psychologists argue it may well be that there was once an evolutionary advantage to having all the women in a community menstruate at approximately the same time.
Evolutionary argument for menstrual synchrony
Point: Menstrual synchrony has an evolutionary value. If women fall pregnant around the same time new-born babies can be cared for collectively within a social group, which increases chances of survival.
Evidence: However, the validity of this evolutionary perspective has been questioned. Schank (2004) argued that too many women cycling together wll increase competition for the best males.
Explain: As the competition is so high, some of them will miss out.
Point: Therefre it is uncertain whether synchronous menstrual cycles has the evoulutionary value that has been claimed.
Menstruation and exogenous zeitgebers.
What evidence is there to support the suggestion that menstruation is govered by exogenous zeitgebers?
Point: a strength of the explanation that the menstrual cycle is , to sme extent, governed by exogenous zeitgebers is that there is supportive evidence.
Evidence: Reinberg(1967) examined a woman who spent three months in a cave with only a small lamp to provide light. Reinberg noted that her menstrual cycle shortened from the usual 28 days to 25.7 days.
Explain: this result suggests that the lack of light (an exogenous zeitgeber) in the cave affected her menstrual cycle.
Link: therefore this demonstates the effect of external factors on infradian rhythms.
Give an example of, and describe the clinical presentation of a psychological disorder that has an infradian rhythm.
- Seasonal Affective Disorder
- SAD is a depressive disorder which has a seasonal pattern of onset, and is described and diagnosed as a mental disorder in DSM-5.
- As with other forms of depression the main symptoms of SAD are persistent low mood alongside a general lack of activity and interest in life.
What biological rhythm does this disorder follow?
- SAD is often refererred to as the winter blues as the symptoms are triggered during the winter months when the number of daylight hours becomes shorter.
- SAD is a particular type of infradian rhythm called a circannual rhythm as it is subject to a yearly cycle.
What is a potential mechanism for this disorder?
- It is believed that the hormone melatonin is implicated in the cause of SAD. During the night, the pineal gland secretes melatonin until dawn when there is an increase in light. During winter, the lack of light i=the morning means the secretion process continues for longer. This is thought to have a knock-on effect on the production of serotonin in the brain – the neurotransmitter that is linked to depression.
Outline a study that would cast doubt on the impact of an exogenous zeitgeber on seasonal affective disorder
Point: One limitation of the explanation that the exogenous zeitgeber of light affects the infradian rhythm of SAD is that there is mixed evidence.
EVIDENCE: - One of the most effective treatments for SAD is phototherapy.
This is a lightbox that stimulates very strong light in the morning and evening. It is thought to reset melatonin levels in people with SAD. Eastman et al. (1998) found that this relieves symptoms in 60% of sufferers. However, the same study recorded a placebo effect of 30% using a fake generator.
EXPLAIN: - If SAD was solely due to biology (an infradian rhythm), then the fake generator would not have caused a relief in symptoms in the fake generator.
LINK: - This casts doubt on the chemical influence of phototherapy and suggests that SAD may also be influenced by psychological factors.
Outline a limitation of therapy for seasonal affective disorder
POINT: - One limitation of SAD therapy is that its effects may be short term.
EVIDENCE: - Sanassi (2014) found that light therapy reduced symptoms of SAD in 80% of people.
EXPLAIN: - However, Rohan et al. (2009) recorded a relapse rate of 46% over successive winters, compared to 27% in a comparison group receiving CBT.
LINK: - This suggests that light therapy may be an effective short - term treatment but additional treatments may be required if benefits are to be maintained.
