> There are no known health problems caused by this syndrome

This is a causal hypothesis framed as a statement. The rhetorics indicate an authoritative statement of fact regarding what the syndrome does cause, which is fundamentally an impossible conclusion to draw empirically.

The only hedge in the sentence is "known", which is tautological.

Of course, it's impossible to eliminate all variables, making authoritative claims about lack of causal relation impossible. But at least they could make the effort to frame this uncertainty in reasonable terms.

> What would the causal hypothesis be, "this syndrome causes no diseases"?

EDIT: but c'mon, just read the article. It's extremely bold in its claims with no evidence. "If you have short sleeper syndrome, you don’t need as much sleep as others. You can expect this to continue throughout your life." "Natural short sleepers don’t experience the same health risks as people who don’t get enough sleep." etc. I don't see any semantic difference between this and "this syndrome causes no known diseases". (or "SSS doesn’t pose any known health risks." as the actual quotation states.)