I have recently read a paper about how stress affects morning salivary cortisol levels in an individual. I am conducting a study on monozygotic twins and was wondering if cortisol levels would fluctuate similarly in a pair of twins, or whether cortisol and other hormones are unrelated to the genetic makeup of the twins.
1 Answer
Bartels et al. 2003 is a review that reports an estimate of the heritability of the cortisol level of 0.62. In comparison to most traits, it is a relatively high heritability.
So, in short, the answer is "no". Cortisol level variation is lower among twins than among unrelated individuals. If the definition of heritability is a little bit unclear to you, you should have a look at this post.
The reaction norm of cortisol level (and other stress response) with varying stress level also seems to be heritable (Ilsing and Hoelsboer 2006, Volckaert et al. 2012).
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1$\begingroup$ "So, no cortisol level variation is lower among twins than among unrelated individuals"... I believe you're missing a comma after the no, am I right? $\endgroup$– user24284Commented May 15, 2017 at 1:39
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1$\begingroup$ Yes indeed! A comma changes everything! Thanks $\endgroup$– Remi.bCommented May 15, 2017 at 2:48
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$\begingroup$ No worries, already upvoted anyway! $\endgroup$– user24284Commented May 15, 2017 at 3:20