Isn't this sort of a chicken-egg problem? I have horrible sleep issues, but they're caused by PTSD related anxiety, and yes, the insomnia then exacerbates the anxiety. I sleep better when my anxiety is under control, but it's not the good sleep that reduces my anxiety--- it's stuff like Xanax and meditation.
I think that is an important construct. It allows us to abstract the notion of an individual and make it something well above a bag of bones and meat. By "above" I mean something superior, trancendant, more important.
A lot of religions have the concept of a soul, and due to Abrahahim religions, the West that concept persisted. Even if people don't believe in a soul there is still a concept of a mind as separate from the body.
In computer terms (because it is hacker news), there is a tempting analogy of software and hardware. The mind / self / personality / soul is the software. The body is the hardware. Of course, we know that software is stored by altering some parts of the hardware (electric charges, etc)). So there is a connection obviously, but we still talk about it as separate things.
It seems like our consciousness is constructed in such a way that it's very easy for people to forget that we actually have a body connected to our head.
Another interesting idea would be to think that mental health problems in part are caused by the systems inside our body that are outside of our conscious control not working properly communicating their discomfort as mental health problems.
I'm a clinical psychologist and I don't think I've had a patient in therapy who had
1. Sleep 2. Exercise 3. Stress 4. Food
Figured out.
What I mostly notice is that once these things are improved the need for therapy diminish significantly.