I suspect there's a lot to it. I hope to get research going to see if anhedonia is possibly some sort of advanced survival mechanism that can be switched on or is activated by (some) humans to conserve energy in times of crisis - eg. famines.
Pleasure is a very complex area. What we often describe as pleasure, particularly in basic requirements of existence - is no more than relief. Identifying what is primal and what 'seems' to be primal is difficult enough, then, to analyse the emotions that come when needs or wants are satisfied are a very complex layer on top of that.
