anorexia and genetics Flashcards
what is anorexia?
an eating disorder in which a person is obsessed with weight, body shape and food intake to the point of self-imposed starvation
what are the symptoms of anorexia?
1) restriction of energy intake resulting in body weight being significantly below what would be expected based on the patient’s age and height.
2) an intense fear of gaining weight or participating in persistent behaviour that will interrupt the gaining of weight even though current body weight is very low e.g. large amount of exercise
3) distortion in body image where the body weight is hugely overestimated and the patient is unable to accept the severity of the low body weight
what are the features of anorexia?
- there are two types: restricting type and binge-eating type
- the restricting type will show weight loss through dieting, excessive exercise or fasting
- the bingeeating type will have reccurent bouts of bing-eating with purging, self induced vomiting, misuse of laxitives
- onset before puberty or after 40 is rare
- more females are diagnosed than males (10:1)
- amenorrhoea can occur in females
- higher prevalance in MEDCs
what is the research from Grice et al?
studied 192 families where one member had received a diagnosis of AN and at least one other member had been diagnosed with another form of an eating disorder.
- when they focused on a subgroup of ppts (37 fams) where at least 2 relatives had been diagnosed with the restrictive type of AN
- there was strong evidence for a susceptibility gene on chromosome 1 as similar markers were found in the afflicted families
what did Van Zeeland find?
found that when comparing 152 different genes in a sample of women with AN and another group without the disorder, there were significant differences in and around the EPHX2.
- the EPHX2 gene is associated with production of an enzyme that metabolises cholestrol suggesting that the disorder may be caused by disruption in how the body processes cholestrol.
what supports the findings of Van Zeeland?
comes from observations that often patients with anorexia have higher cholestrol than expected considering may of them are severly malnourished and in some cases such as in some patients with depression, weight loss can lead to an increase in cholestrol levels
what is a strength of the genetic explanation?
there is evidential support of genetic explanation however it is not clear about the extent to which genes can explain the cause of the disorder.
- there is evidence that people with relatives with eating disorder, have an increased risk of eating disorder
- however many of these family members will have spent a lot of time together in the same environment
what is a weakness of the genetic explanation?
it is difficult to separate out the biological explanation as a cause of AN as opposed to being a result of the disorder.
- the causal factors are difficult to determine as AN is so complex
