Studies: One contemporary study on another disorder, from the following: Anorexia — Edexcel A-Level Psychology
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Studies: One contemporary study on another disorder, from the following: Anorexia explained
Twin and family work puts the heritability of this eating disorder high, yet no specific gene had been pinned down, so the team sequenced well over a hundred candidate genes in around twelve hundred women with the diagnosis and a larger control group, then tested the promising variants again in independent samples. Variants in EPHX2, the gene coding for an enzyme used in the metabolism of fats and cholesterol, were associated with the disorder and the association replicated, and in a general population cohort the same variants altered the usual relationship between body weight and cholesterol level. That points towards metabolic regulation rather than appetite alone, and it is the strongest single piece of evidence for the nature side of the debate in this topic.
5.3.6 Guardia et al. (2012) Imagining One’s Own and Someone Else’s Body Actions: Dissociation in Anorexia Nervosa.
Distorted body size is usually measured by asking patients how wide they look, which invites self report bias, so this study measured it through action instead. Women with the restrictive form of the eating disorder and matched healthy women faced a doorway like opening of varying width and judged whether a body could pass through, once imagining themselves and once imagining the experimenter. Controls judged both bodies accurately. The patients judged the experimenter accurately too, but rejected openings that were comfortably wide for their own shoulders, so the overestimation was specific to the self and appeared in the body schema that guides movement rather than in perception generally. That dissociation is the finding to quote, and the small clinical sample is the limitation.
Your focus
- 5.3.5 Scott-Van Zeeland et al. (2013) Evidence for the role of EPHX2 gene variants in anorexia nervosa.
- 5.3.6 Guardia et al. (2012) Imagining One’s Own and Someone Else’s Body Actions: Dissociation in Anorexia Nervosa.
Studies: One contemporary study on another disorder, from the following: Anorexia exam tips
Marking Points
- Describe the design as a case control genetic association study with a discovery stage and a replication stage, comparing the sequence of selected candidate genes in diagnosed women against controls, which is correlational and not an experiment.
- Name the finding: variants in EPHX2 were more common in the cases, the result held in independent samples, and the enzyme the gene codes for is involved in handling fats rather than in appetite.
- Say why replication carries the argument, because a single association in a study testing many variants is very likely to be a chance finding, so credit goes to the independent confirmation and to the population cohort result linking the variants to cholesterol.
- Evaluate the strengths honestly: a large sample, objective genetic data rather than self report, and an unexpected biological pathway that generates testable predictions.
- Evaluate the limits: the variants explain only a small share of risk, most carriers never develop the disorder, the sample is overwhelmingly female and of European descent, and starvation itself changes metabolism, so cause and consequence cannot be separated by a study of this shape.
- Describe the task and its measure: the width of the opening at which passage is judged possible, expressed as a ratio to the judged person shoulder width, and compared with the ratio actually needed to pass, which turns a subjective belief into a number.
- Name the design as a comparison of an independent clinical group with matched healthy controls, with the perspective taken, own body or another body, varied within each participant.
- Report the dissociation precisely, that patients were accurate for the experimenter and inaccurate for themselves, because a summary saying they overestimated body size loses the whole point of the study.
- Explain what it implies: the distortion is embodied and self specific, sitting in the representation the brain uses to plan movement, which supports treatments that work through action and exposure rather than through argument about appearance.
- Evaluate: an objective behavioural measure and matched controls are strengths, while a small sample of female inpatients with one subtype, a laboratory task using imagination rather than real movement, and the impossibility of knowing whether the distortion preceded or followed starvation are the limits.
Examiner Tips
- 💡Pair it with a psychological or social explanation of the disorder, because essays here almost always want an interactionist conclusion rather than a purely biological one.
- 💡It is the obvious anchor study for nature and nurture and for socially sensitive research in the issues and debates section, so learn it as evidence in two places at once.
- 💡Describe questions follow aim, method, results and conclusion, so rehearse those four in order and resist the urge to evaluate until the command word asks you to.
- 💡If asked about the usefulness of the research, talk about identifying people at risk and about the possibility of treatments aimed at metabolism, then say plainly what a small effect size cannot deliver.
- 💡A strong choice when a question asks about operationalisation or ecological validity, because you can explain exactly how an abstract idea was turned into a measurable judgement.
- 💡For a compare question on the two contemporary studies of this disorder, set the behavioural laboratory method against the genetic association study on sample, data type and level of explanation.
- 💡Evaluation marks follow specific points, so avoid saying only that the sample was small, and add who was in it and why that matters for generalisation.
- 💡Keep a sentence on application, since the finding is used to justify mirror exposure and virtual reality work aimed at the self specific distortion.
Common Mistakes
- Writing that the study found the gene for anorexia nervosa. It found common variants associated with raised risk, which is a very different claim.
- Using the result as proof of biological determinism while ignoring that a genetic vulnerability needs an environment to act in, which is the diathesis stress point the examiner is looking for.
- Leaving out the control group or the replication when describing the method, which are the two features that make the study worth prescribing.
- Explaining the gene as controlling hunger or appetite, when the enzyme belongs to lipid metabolism.
- Forgetting that this is socially sensitive research, so saying nothing about stigma, genetic screening or the way families read a genetic finding as blame or as absolution.
- Saying the patients overestimated everyone body size. They were accurate about the experimenter, and the contrast is the result.
- Describing the study as a questionnaire or interview about body image, when the whole design exists to avoid self report.
- Omitting the control group or the matching, which removes the comparison that makes the finding interpretable.
- Concluding that distorted body schema causes the disorder, when the participants were already ill and severely underweight when tested.
- Treating imagined passage as the same as real passage, and so overstating how far the result transfers to moving through the world.