Infradian Rhythms

Specification

Infradian rhythms including the menstrual cycle and seasonal affective disorder and therapies, including light therapy.
Research into infradian rhythms.

The Menstrual Cycle

Infradian rhythms have a cycle of more than 24 hours, with the female menstrual cycle lasting for about 28 days. The pituitary gland releases FSH to stimulate the ovaries to produce eggs. After the ovulatory phase, progesterone levels increase in preparation for the possible implantation of an embryo in the uterus. It is also important to note that although the usual menstrual cycle is around 28 days, there is considerable variation, with some women experiencing a short cycle of 23 days and others experiencing longer cycles of up to 36 days.

The hormone oestrogen is at its lowest on the first day of the menstrual cycle, and gradually increases during the cycle as the eggs mature. If the egg is not fertilised the levels of oestrogen and progesterone decline, so leading to the lining in the womb being shed.

The fluctuation in oestrogen and progesterone levels are thought to be the cause of PMS. This may include symptoms such as mood disruption or becoming angry at situations that would not normally affect them. Dalton found that PMS was associated with an increase in accidents, suicides and crime.

Evaluation

Research suggests that the menstrual cycle is, to some extent, governed by exogenous zeitgebers (external factors). 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. This result suggests that the lack of light (an exogenous zeitgeber) in the cave affected her menstrual cycle, and therefore this demonstrates the effect of external factors on infradian rhythms.
There is further evidence to suggest that exogenous zeitgebers can affect infradian rhythms. Russell et al. (1980) found that female menstrual cycles became synchronised with other females through odour exposure. In one study, sweat samples from one group of women were rubbed onto the upper lip of another group. Despite the fact that the two groups were separate, their menstrual cycles synchronised. This suggests that the synchronisation of menstrual cycles can be affected by pheromones, which have an effect on people nearby rather than on the person producing them. These findings indicate that external factors must be taken into consideration when investigating infradian rhythms and that perhaps a more holistic approach should be taken, as opposed to a reductionist approach that considers only endogenous influences.
Evolutionary psychologists claim that the synchronised menstrual cycle provides an evolutionary advantage for groups of women, as the synchronisation of pregnancies means that childcare can be shared among multiple mothers who have children at the same time.
There is research to suggest that infradian rhythms such as the menstrual cycle are also important regulators of behaviour. Penton-Volk et al. (1999) found that woman expressed a preference for feminised faces at the least fertile stage of their menstrual cycle, and for a more masculine face at their most fertile point. These findings indicate that women’s sexual behaviour is motivated by their infradian rhythms, highlighting the importance of studying infradian rhythms in relation to human behaviour.
It is hard to separate infradian rhythms from all external zeitgebers therefore research may not be valid when isolating the infradian rhythms.

Seasonal Affective Disorder

Seasonal affective disorder is an infradian rhythm as it lasts for about a year. As the winter months are darker the levels of melatonin in the body increase, leading to feeling more tired. Lack of sunlight can lead to a reduction in serotonin, which will decrease a person’s mood. The reduction of daylight in the winter may cause disruption to circadian rhythms and so affect the sleep wake cycle.

Evaluation

Evidence supports the role of melatonin in SAD. Terman (1988) found that the rate of SAD is more common in Northern countries where the winter nights are longer. For example, Terman found that SAD affects roughly 10% of people living in New Hampshire (a northern part of the US) and only 2% of residents in southern Florida. These results suggest that SAD is in part affected by light (exogenous zeitgeber) that results in increased levels of melatonin.
Understanding the role of darkness in SAD has led to the development of phototherapy to treat SAD. SAD sufferers have reported that daily use is enough to relieve them of lethargy, depression and other symptoms.
Zhang et al. (2016) found that giving mice, who had a rare variance on the circadian clock gene, light at different times of day affected their sleep wake cycle.
Sandman et al. (2016) found participants who had seasonal affective disorder were more likely to suffer from insomnia, so it may be the lack of sleep that causes the depression rather than bodily rhythms.
Knowing that a lack of light may lead to seasonal affective disorder has led to light therapy being used to treat it, so it has application.
Palinkas et al. (2004) said that it was the social environment that had more of an effect on mood disorders on participants who spent the winter in the Antarctic rather than the physical environment.

Light Therapy

Light therapy decreases the level of melatonin by using a light box to increase the amount of light received, the decrease in melatonin will reduce the sleepiness felt by the patient so should be effective in helping reduce the symptoms.

Strong lights (6000-10000 lux equivalent to daylight) are used in the evening and/or morning. The user would have to sit under a light box for 30 to 60 minutes. They could also use a dawn simulator which gradually increases the light in the morning just before waking up.

Evaluation

Light therapy aims to treat the symptoms of seasonal affective disorder whilst CBT tries to change our thought processes, therefore CBT should last long term so is more effective as it does not just try and get rid of the symptoms but addresses the reasons behind the symptoms.
Alternative treatment is an anti-depressants such as SSRIs. SSRIs will increase the serotonin in the brain and help improve her mood during the winter months. They will stop serotonin from being taken out of the synapse by uptake mechanisms. You take SSRI as a tablet, starting at the lowest dose possible to improve her feelings of depression.
Light therapy can have mild side effects such as insomnia which can affect patients negatively.
Light therapy cannot be used if someone has eye conditions as it could aggravate the eye condition further.
Eastman (1988) found that after 3 weeks symptoms of Seasonal Affective Disorder had decreased significantly with light therapy.
Psychotherapy has fewer physiological side effects so it may be less distressing to patients than other treatments.
Psychotherapy may take up to 6 weeks to begin to be effective.
Antidepressant selective serotonin reuptake inhibitors (SSRI’s) can be used to prevent Seasonal Affective Disorder prior to onset.

Past Paper Questions

2 Markers

Describe one psychological symptom that may be experienced during menstruation. (2) January 2017
Explain one reason why light therapy may be considered an effective treatment for seasonal affective disorder. (2) January 2019
Explain one difference between the use of light therapy and the use of one other therapy for seasonal affective disorder. (2) January 2019

3 Markers

Lysander is undergoing light therapy for his seasonal affective disorder. He finds that in the winter he no longer wants to play football and spends more time in bed. Identify three symptoms of seasonal affective disorder that Lysander may have. (3) June 2017
Describe how light therapy would be used as a treatment for Lysander’s seasonal affective disorder. (3) June 2017
Kylie experiences seasonal affective disorder. When it is winter time she feels more depressed and no longer feels pleasure when doing activities she enjoys in the summer time. She often wants to stay in bed. Kylie researched biological explanations about why she experiences seasonal affective disorder every year. Describe why Kylie experiences seasonal affective disorder. (3) January 2019

4 Markers

Beryl’s menstrual cycle lasts, on average, 30 days. She finds that towards the end of her menstrual cycle she becomes more argumentative with her friends. Describe the menstrual cycle in relation to Beryl. (4) January 2018
Maria found that when she went to university her menstrual cycle synchronised with the menstrual cycles of the female students she lived with. Describe why Maria’s menstrual cycle synchronised with the female students she lived with. (4) January 2017
Describe the role of infradian rhythms in explaining human behaviour. (4) June 2016
Describe one therapy, other than light therapy, that Aya could use for her seasonal affective disorder. (4) January 2020

8 Marker

Evaluate the role of infradian rhythms on the menstrual cycle. (8) October 2018

12 Marker

Evaluate research into infradian rhythms. (12) January 2018
To what extent does light therapy work effectively for people diagnosed with seasonal affective disorder? (12) June 2018
Evaluate the role of infradian rhythms in human behaviour. (12) January 2020
Evaluate the role of bodily rhythms in explaining Rosa’s seasonal affective disorder. (12) October 2019

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