I intuitively agree that optimal sleep and exercise and diet and screen time probably make a difference to wellbeing, but am I alone in thinking that trying to determine a "link" between these things is lazy, easy, obvious and just wholly inadequate?

We want to know, definitively, what are causes and effects. I appreciate that's hard. But why waste so much time and money just trying to establish "links" which are fundamentally just correlations.

It's like admitting causation is hard, just aim instead for correlation - and call it quits after getting some headlines and maybe more funding...