Just want to point this out - I am diagnosed with both of these and some other things. But what I think is a lot of the problem is that when I go to declutter, my ADHD brain is so distracted and then it "freezes" - more so under pressure. I just went through a horrendous move and about had a breakdown, because of the time pressure. It has opened my eyes to the reality that at my age I can't put off resolving the hoarding problem any longer. And I WANT to get it taken care of, more than ever. I just hope I can get it done without blowing my brain's circuits or falling into depression. I'm going to do my best to be positive about it, but I know it's going to be a challenge.
One more word about ADHD folks - so many of us are the "right brained" creative types and we can see so many possibilities for our "junk" - art projects, etc. and we have many interests. You could hand us a widget from the hardware store and we could write down 100 uses for it. This works against us when it's necessary to decide that we can live without said widget.
What is helpful? Giving it to someone else, recycling, even a silly "saying goodbye" to it ritual - yes, I did this! I "thanked" a box of cardboard pieces for the dreams of potential future art projects I had been intending to do with them. Then I was able to hand the boxful to my friend who would recycle them. :) I don't care how crazy a strategy sounds if it works.