eval infradian rhthyms Flashcards
Real-world application
One of the most effective treatments for seasonal affective disorder (SAD) is light therapy, a box which simulates very strong light to reset the body’s internal clock. Studies show this helps reduce the effects of SAD (e.g. excessive sleepiness) in about 80% of people with the condition (Sanassi 2014). That sounds like a very high rate of success. Light therapy is also preferred over antidepressants in the treatment of SAD because it is regarded as safe with no dangerous side effects or risk of tolerance and/or dependence over time.
That said, light therapy can produce headaches and eye strain. The bright light can be quite intense and some people may find this aspect uncomfortable. Perhaps more tellingly, a study by Kelly Rohan et al. (2009) suggests that the positive effects of light therapy wear off over time. Her study recorded a relapse rate of 46% over successive winters, compared to 27% in a comparison group receiving CBT. This suggests that, although light therapy may be effective for the first few months, maybe the positive effects may wear off as the person becomes used to it.
This suggests that light therapy may be an effective short-term treatment but additional treatments may be required if benefits are to be maintained.
Evaluation
Evolutionary basis
One strength of menstrual synchrony research is that it may be explained by natural selection.
Synchronisation of the menstrual cycle, of the kind observed in the Stern and McClintock study (facing page), is thought by some to have evolutionary value. For our distant ancestors it may have been advantageous for women to menstruate together and become pregnant at the same time. in a social group, this would allow babies who had lost their mothers during or after childbirth to have access to breast milk, thereby improving their chances of survival.
This suggests that synchronisation is an adaptive strategy.
Methodological limitations
One limitation of synchronisation studies is their methodological shortcomings.
There are many factors that may effect change to the menstrual cycle, including stress, changes in diet, exercise, etc. These may ac as confounding variables, which means that any supposed pattern of synchronisation is no more than would have been expected to occur by chance. This may explain why other studies (e.g. Trevathan et al. 1993) have failed to replicate the findings.
This suggests that menstrual synchrony studies are flawed.
