Right. The remaining possibility is the third variable. Membership in certain populations may be associated with increased likelihood of becoming a sex worker and also of experiencing difficulties that you are suggested are caused directly by being a sex worker. Such difficulties may appear after someone has become a sex worker, even while having an independence cause.
Sure, but that is true for ever job then. An unknown and hidden confounding factor explaining job choice and the problems of the job can always exist.
Police officer or fire fighter aren’t actually dangerous. It is simply that people who are more likely to make bad decisions that get them killed also are those that choose to be police officer or fire fighters.
Burnout does not affect teachers with higher probability than it affects hairdressers. It is because people who get burnouts are also the people who choose to be teachers.
Sure, but that is true for ever job then. An unknown and hidden confounding factor explaining job choice and the problems of the job can always exist.
The general principle may apply to any job, but you wanted to study the population of sex workers in particular, and doing so requires collecting and analyzing data, in regard to sex workers, properly and sufficiently, toward a conclusion.
I only suggested that your conclusion may not be robust if sex work is disproportionately represented by populations that carry broader vulnerabilities to some of the difficulties that you inferred were directly consequences of sex work.
