In scientific research we often find information about comorbidity. For example, in Tobin & Griffing 1996 about eating disorders we read: "Abused patients were not only more disturbed on comorbid psychiatric symptoms, but were more likely to have engaged in self-injurious behavior (80%) and attempted suicide".
The main purpose of such comorbidity information is diagnostics. But can we use this information at least as some hint about possible reasons? This seems possible:
First, it shows some correlation between "sexual abuse" and "attempted suicide". This adds evidence to the general thesis that there is some relation between "sexual abuse" and "attempted suicide".
But it is also a very special one. It means that such a correlation exist for a very special subgroup considered in this paper - here women with eating disorders.
This special information may be useful to test some theories and to get indirect support for or against some hypotheses.
For example, let's consider different types of abuse. We may suspect that different types of abuse lead to different impact. Now, if our hypothesis is that two different diseases are caused by the same type of abuse, our hypothesis suggests high comorbidity. If the two diseases are caused by different types of abuse, there will be low comorbidity.
In this sense, if high comorbidity between two diseases is mentioned, this is some evidence in favour of the thesis that the same type of abuse causes the two diseases.
This may be useful especially if there is already some information about the type of abuse which causes one of them.