Reference(s):
- Main Reference: Holliday, J., K. Tchanturia, et al. (2005). "Is impaired set-shifting an endophenotype of anorexia nervosa?" Am J Psychiatry 162(12): 2269-75.
- Background Reference: Treasure, J. L. (2007). "Getting beneath the phenotype of anorexia nervosa: the search for viable endophenotypes and genotypes." Can J Psychiatry 52(4): 212-9.
- Bulik, C. M., Hebebrand, J., Keski-Rahkonen, A., Klump, K. L., Reichborn-Kjennerud, T., Mazzeo, S. E., et al. (2007). Genetic epidemiology, endophenotypes, and eating disorder classification. Int J Eat Disord, 40 Suppl, S52-60.
Article(s):
Holliday Is Impaired Set-Shifting an Endophenotype of AN.pdf- Treasure Getting Beneath the Phenotype.pdf
- Bulik Genetic Epidemiology Endophenotypes and ED Classification.pdf
Discussion:
Beth led a very nice discussion on the nature of endophenotypes, set-shifting, and the tasks discussed in the Holliday paper.
Endophenotypes are traits thought to contribute to vulnerability to illness by conferring risk. To be an endophenotype, a trait or characteristic must be:
- state independent (i.e., present in patients before illness onset and/or after illness resolution)
- cosegrated with illness (patients have the trait more than the general population)
- heritable
- non-affected family members have the traits at greater frequencies than in the general population (i.e., there is a dose-response relationship between the amount of genetic loading and the expression of the trait)
Set-shifting in AN is a good candidate for an endophenotype, because conditions 1 and 2 above have been demonstrated. This paper sought to demonstrate that the 4th criterion also applied, and for the most part, it succeeds in making that demonstration.
Questions arising from the discussion:
- what is the set-shifting literature in BN?
- does the maudsley O/C inventory measure O/C personality traits (i.e., is it sensitive for OCPD, or only for OCD)?
- how does one establish cause between a putative endophenotype and the illness itself beyond simple coaggregation in patients and first-degree relatives
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Next time we will discuss the Iowa Gambling Task in AN. I will post more details soon.
Graham