-One difficulty with studies of anorexia is that the actual diagnosis in any individual is not that certain. Some individuals suffer both anorexia and bulimia, though not always at the same time. This means that the genetic susceptibility may be to 'develop eating disorders' rather than anorexia in particular. Gorwood et al (1988) suggest that if we want to identify the genetic causes of anorexia, we need to identify the distinct subtypes more clearly.
-Twins don't just share the same genes - they also share cultural and family values, and the environment for MZ twins is more similar than for DZ twins. Therefore, physiological and environmental factors are confounded. Indeed, the 56% concordance rate in MZs might be entirely due to their more similar upbringing than DZs.
However, Holland et al argue that MZ twins who actually look very different still have the same high concordance rates as MZ twins who look identical.
-Small sample - many twin studies involve a small sample size. Holland et al studied only 25 MZ and 20 DZ twins, and it is estimated that 15,000 pairs would be needed for a definitive, genetic study. The low occurrence of both twin births and eating disorders make this unlikely.
-McClelland & Crisp (2001) found a higher incidence of AN in social classes 1 and 2. They reject the idea that this is due to higher referral levels and suggest it's due to an avoidance response to adolescent conflict within such families. Why does this challenge the findings of Holland et al?
-There may be reasons why twins are more prone to mental illness than non-twins and therefore the findings may not be generalisable to the rest of the population. It is possible that twins may be subject to greater developmental difficulties (e.g. sense of identity) - or that they are genetically more vulnerable than other adolescents.
-Why can't the study fully explain anorexia in terms of genetics? Additionally, can the study explain the dramatic increase of cases of AN in the last 30 years?
-Proposes that the typical AN symptoms of food restriction, hyperactivity and denial of starvation, reflect the operation of adaptive mechanisms that once caused migration in response to local famine conditions. Normally, when a person begins to lose weight, physiology mechanisms conserve energy and increase desire for food. These adaptions facilitate survival in hard times. However, among ancestral nomadic foragers, when extreme weight loss was due to a severe depletion of local food resources, this adaption must be turned off so that individuals can increase their chances of survival by migrating to a more favourable environment. Food restriction is a common feature of many species when feeding competes with other activities such as migration or breeding. During the Middle Ages, the phenomenon of 'holy anorexia' was widespread among pious women. The hyperactivity typically found in anorexics may be a form of 'migratory restlessness' as many species increase activity in times of food shortage and prior to migration. In the EEA those starving foragers who deceived themselves about their physical condition would have been more confident about moving on to a more favourable (in terms of food availability) environment, and so would have been more likely to survive. Therefore, for modern-day individuals, among those who are genetically vulnerable to AN, losing too much weight may trigger these ancestral mechanisms.
-Method: Discussion groups were set up across the UK to explore factors that might affect the food choices of girls and young women of African and South Asian descent. The discussions were analysed using content analysis.
-Results: A number of common concerns were voiced by the women. Food choices were indeed influenced by culture, time, availability, cost, health and price.
*Pakistani/Bangladeshi women's cooking skills appeared to have been learnt from the older generation of females in the family, and they also took pride in their traditional cooking.
*All the women surveyed appeared to have low levels of western food in their diets. However, they appeared to adopt the less healthy aspects of the western diet including fried fish, pizza, chips and fatty snack foods. However, these were mainly chosen to give people a change or when preparation time available was short.
*The Pakistani/Bangladeshi women expressed the opinion that their diet had become less healthy following the adoption of the worst of the British diet!
*The women did make a link between food and health; however, cultural background and knowledge influenced this.
*Pakistani/Bangladeshi women generally appeared to have quite a good understanding of what food and methods of cooking are healthy and unhealthy. However, this knowledge did not appear to translate consistently into dietary choices.
*Zimbabwean women noted that in Zimbabwe nobody worried about being slim, but now that they were in the UK there was more pressure to be slim.
-Conclusion: many issues that affect the food choice of people who move to the UK are common within different ethnic groups.