There is a picture in front of me of latent growth model example. Latent variables estimated by the calculations are Intercept and Linear Slope. That is fine. However, they are calculated based on PTSD across numerous time points. And PTSD is marked in squares indicating observed items.
My doubt is usually in CFA concepts such as depression, anxiety, and so on were latent and based on observed items. I do not think this model suggests that PTSD is measured by one observed item... so why is it observed?
Thank you
You can fit multilevel models within SEM, so, the model is probably equivalent to a linear mixed model. See Joop Hox's book for some examples:
http://www.joophox.net/publist/Chap14ProofsX.pdf
This can be due to the fact that the final score is calculated based on the average of the several observed variables (items of the scale)
The following is more of a theoretical answer to your question. Certainly, there are challenges during developmental stages, e.g. from infancy where I get most everything I want to toddlerhood where I get very little of what I want (because simply I want more), into early childhood where I am one of 30 kids in the class cf. 2 or 3 at home, and then into adolescence with all its storm and stress. Each of these stages is ripe for trauma, and as the EMDR folks say, trauma is an unexpected event in which I have emotions I am not able to feel, express, and resolve.
I think that what is construct conceptually is only partially overlapping with how one uses it in statistical terms. So, in the case of the example that you mention, I would like to know what is the latent variable assumed to be measured by the "observed" PTSD? In a different setting (or question), one could also use PTSD as a latent variable deriving from a different set of observed variables.
Try my paper with Gan and Koczkdaj...
You may also check in Wikipedia who was reading his paper:
http://www.cs.laurentian.ca/wkoczkodaj/p/ArrowReadsParadox.pdf
PTSD as measured by the DSM until the changes with the recent version focused on 3 symptom clusters; intrusion(e.g. flashbacks) avoidance(e.g. numbness) and arousal. The 3 clusters are related yet have some independence in the therapy process. For instance as avoidance goes down arousal often increases.
PTSD is at heart a dysregulation of ones Neurobiological system. Yet this disruption is not static. What the person experiences with PTSD when their system is stuck on high is neurobiologically and thus emotionally, behaviorally and somatically quite different then when they are stuck on low (parasympathetic overload).
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