This is a very difficult question to answer without reading more of this paragraph or article. It seems like this comes from some academic journal, or maybe a study on stress?
I will give you my guesses, and I hope they help!
This sentence seems like what I would call a "qualifier," or something that a writer uses to help explain the limitations of an experiment or study. In this case, the writer is saying how difficult it is to study chronic stress, and what causes stress, when you include what he/she calls "role occupancy."
Role occupancy, here, is how someone labels themselves in a relationship. When I say relationship, I don't mean a romantic one, by the way. I mean any relationship between people. The writer lists a few: spouse, worker, parent. A spouse means a romantic relationship. A worker means a relationship between an employee and an employer. A parent, of course, is a relationship between a mother/father and child.
The writer is saying that there is a big problem with saying that one type of role is tied to one type of stress, basically. He/she is pointing out a flaw in that way of viewing the causes of stress.
Hope that helps!