And here on the other side is very convincing evidence that the moon phase can have pronounced effects on sleep

https://www.science.org/doi/10.1126/sciadv.abe0465

And the literature about how sleep affects mental health is legion.

So it's not at all nonsense, the effect size might be small. You might not see it at all in hospitals because the lighting in hospitals isolates you from the moon.

It is really easy to be swayed by anecdotes and equally easy to be swayed by a little scientific evidence to the contrary.

I am comfortable with saying that light keeps us from sleeping.