In the field of intellectual disability, data are often hierarchical. As in the case of the classic example of schools (school, class, student), data in our field are often hierarchical ( residential setting, life unit, individuals).
In this context, I am looking for studies that have analyzed the impact of this hierarchy in the field of intellectual disability or empirical studies that have at least controlled for this using multilevel models.
is anyone aware of the existence of such studies?
Dear Claudio,
We have done work on intellectual disability using multilevel models, although in a somewhat different methodological context that what you are proposing. We recognised in our models that individuals may have been part of the same biological family (i.e. full siblings) thereby taking into account unobserved familial confounders such as shared genetic material, similar fetal environments, similar early life environment etc. We therefore treated the family unit as a potential source of confounding and focused only on the within-family estimate in our analyses (i.e. differences in ID outcomes between full siblings who were discordant in exposure).
Having said this, the modeling framework is easily extendable to a full multilevel analysis where other levels may be of interest, e.g. child within family within ethnic group, and effects are quantified across those levels. If you are interested I am happy to share some Stata syntax with you.
Best wishes,
Hein
Just to say that there is now no need for a strict hierarchy with random effects multilevel models. You can analyse cross classifications and multiple membership which can take account of individuals being nested in more than one setting (say in community areas as well as life units) and spending different amounts of time in them. If you do not reflect this reality you can get biased estimates of the contextual effects.
On different types of structures
http://www.bristol.ac.uk/cmm/software/mlwin/mlwin-resources.html#mlmbkgrd
and for technical material on fitting them
http://www.bristol.ac.uk/cmm/software/mlwin/mlwin-resources.html#nonhier
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