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PMS and Neuroticism
Detailed analysis of Aella's data
Aella recently wrote a post about PMS and neuroticism, finding that they correlate at 0.23. Using her own data, I have suggestive evidence that the correlation adjusted for unreliability is somewhere around 0.36.
This is her measurement of PMS symptoms:
She also has a measurement of neuroticism, anxiety, sexual assault, total mental illness, and depression. Using these, one can build a latent variable and see if it correlates with PMS symptoms.
It’s debatable as to whether experiencing sexual assault as an adult counts as an indicator of neuroticism. More neurotic girls are probably more likely to get sexually assaulted, and sexual assault is likely to cause mental harm. Regardless, I would assume a lot of it comes down to luck.
In addition, many girls selected an unusual amount of mental illnesses. I don’t think a girl who selected 10 mental illnesses is much more mentally ill than a girl who selected 5. Because of this, I am winsorizing all girls who selected more than 8 mental illnesses to 8.
Measurement error is something that is important to address, as adjusting for it when doing heritability estimates of personality causes them to increase from about 50% to 80%. I would assume the same applies for normal correlations as well.
Structural Equation Models can be used to adjust for the measurement error that you observe within your data. It does this by modeling latent variable from a set of observed variables, and then relating that variable to other variables. In this article, I use DWLS estimation as several of the variables do not have a normal distribution, so ML yields poor fit statistics.
Here is the summary of the output of different methods used for calculating the correlation between neuroticism and PMS:
Method 1: Structural Equation Model with all 5 mental illness variables.
Result: latent correlation of 0.292
Fit statistics: not great but somewhat passable:
Method 2: Structural Equation Model excluding sexual assault variable
Result: latent correlation of 0.286
Fit statistics: worse than model 1
Method 3: Structural Equation Model excluding mental illness variable
Result: latent correlation of 0.378
Fit statistics: appropriate
Method 4: Structural Equation Model with only neuroticism, anxiety, and depression.
Result: latent correlation of 0.358
Fit statistics: the best
Method 5: calculate MIRT factor score using depression/anxiety/neuroticism then adjust for unreliability
The correlation between general neuroticism and PMS adjusted for unreliability is 0.261/sqrt(0.52)=0.362, roughly the same as the result from the SEM models.
It’s worth noting that this method only corrects for the measurement error inside the data itself. It cannot correct for the fact that self-reports are not always accurate indicators of personality. As such, I suspect the true correlation between latent neuroticism and PMS symptoms is close to 0.5.
Why does neuroticism and PMS correlate?
Aella brought up this finding in the context of the geography of madness, a book which theorizes that many western mental illnesses such as PMS are actually culturally bound syndromes. Alternatively, it could be that hormonal fluctuations experienced during the luteal phase have an amplifying effect on an individual’s personality. Explained graphically: