I think the easiest way is like I wrote "No beating physics."

Seems just as reasonable but less verbose; we appear to get cancer and mental illness with old age regardless of social conditions around us. Physics and entropy win again regardless of the care we put into our semantics.

Regardless my original point was about "long term".

"Marriage staves of mental health" and "a single, long term marriage improves mental health outcomes" are two different things.

Could just be a tight knit quasi-nuclear family social circle is sufficient too but social desirability biases lead is to lean into marriage tradition.