Hypochondria

[terry44]

For most people, it is based entirely in fear.  But I have also seen both of the other possibilities I mentioned.

I must be a notable exception then. I also think that in addition to negativity there may have been an obsessive-compulsive element to it, although getting rid of the negativity cured it for me, even though I still had some fear and OCD for many years after the hypochondria disappeared.

The negativity usually arises as a result of fear.  The OCD is a result of fear.  Hypochondria, OCD and negativity are all just ways in which fear gets expressed.  Different branches of the same tree.

But is interesting that I got rid of the hypochodria by getting rid of a specific negativity, but still had the similar general levels of anxiety and OCD afterwards. Maybe negativity can engender fear or anxiety, just as fear or anxiety can lead to negativity.
The jury seems to be out on the cause of OCD as far as mainstream 'experts' are concerned:
https://www.ocduk.org/ocd/what-causes-ocd/