My mum collects junk. Every room is stuffed full of it. Dad built an extension years ago because the house was too small for us, and then we (my brothers and I) left home, and so she filled the whole place with even more junk. Piled high to the ceiling in every room, with barely room to walk around. She has furniture in her bedroom that has never seen the light of day because it is always covered with piles of clothes and blankets and other tat.
This is definitely an illness; she has no ability to distinguish between something 'collectable' (whatever that means) and something worth collecting. Like most of us can tell the difference between costume jewellry and real valuable jewellry; to my mum it is all the same. All to be kept, and left to gather dust. (It is impossible to keep a cluttered house clean or tidy. Not that she even tries, of course.)
My older brother used to react against this by throwing stuff away, whether it was valuable or not. Years ago he made me throw away my teenage diaries, which I had kept for years, and a journal from a school trip to France that I won a prize for. They all went out. And he threw away his old carry cot from the attic. I still wish we had those things. So the useful stuff got dumped, and the junk remains.
I am very good at sorting through my house twice a year or so, and weeding stuff out, to make room for more stuff. Some goes into the loft, but most goes to the charity shop. And I rescue classic books from the same shops. I don't buy second hand clothes, but I do buy books.
