My cousin suffered from this and to some extent I seem to remember that my Grandmother had some difficulties.
I wanted to read more about it and found some interesting reading online. I don't remember the name of the titles but they weren't hard to find. One book did recommend some form of therapy along with an understanding family member to help get some of the clutter under control.
Others on here have recommended Flylady.net. I read some stuff on her site but found her emails- at the rate of 12 a day pretty hard to keep up with and have any kind of life!!!
Good luck. I understand some of the need to hold onto stuff for fear you'll need it tomorrow. What we found helped with my cousin was to move stuff to a box in the garage. She had 3 days to retrieve anything - and since she usually forgot about it as soon as it was out of sight, her husband got the Kitchen and much of their house under control.
What we found helped with my cousin was to move stuff to a box in the garage.
The good thing about flylady is that you can jump right in. When I joined it a few years ago, I, too was overwhelmed with the emails. I think that was a hurdle I needed to get over, though - learning to delete and begin with the most recent one. :)